The toxicity of caffein : an experimental study on different species of animals

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Title:
The toxicity of caffein : an experimental study on different species of animals
Series Title:
U.S. Dept. of Agriculture. Bureau of Chemistry. Bulletin
Physical Description:
98 p. incl. tables. : ; 23 cm.
Language:
English
Creator:
Salant, William, 1870-1943
Rieger, J. B ( John Benjamin ), b. 1886 ( joint author )
Publisher:
Govt. Print. Off.
Place of Publication:
Washington
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Subjects

Subjects / Keywords:
Caffeine -- Physiological effect   ( lcsh )
Caffein   ( nal )
Caffein   ( nal )
Bulletin (United States. Bureau of Chemistry) ; -- no. 148   ( lcsh )

Notes

General Note:
"Caffein bibliography": p. 97-98.
Statement of Responsibility:
By William Salant and J.B. Rieger.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
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aleph - 029774597
oclc - 13605868
lccn - agr12000679
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lcc - S585|RM666.C2 S3 .A1 no.148
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AA00026027:00001

Full Text


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Issued April 4, 1912.

U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF CHEMISTRY-BU N No. 148.
H. W. WILEY, CHIEF OF BREAU.




THE TOXICITY OF CAFFEIN:


AN EXPERIMENTAL STUDY
ON DIFFERENT SPECIES OF ANIMALS.





BY

WILLIAM SALANT,
ChiefPharmacological Laboratory, Division of Drugs,
AND
J. B. B.RIEGER,
Assistant Chemist.



















WAS HINTON:
GOVERNMENT PRININQ OFFIOE.
1i12















LETTER OF TRANSMITTAL.


U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF CHEMISTY,
Tashington, D. (., November 14, 1911.
SIR: I have the honor to submit for your approval a manuscript
on the toxicity of caffein, which is the first of a series of reports to
be made by Dr. Salant on the pharmacology of this drug; the con-
clusions here reported are, therefore, in some particulars to be
regarded as tentative. The data obtained are primarily of use in the
execution of the food and drugs act, but are capable of much broader
application.
Acknowledgment is made of the assistance rendered by Dr. John
R. Mohler, Chief of the Pathological Division, Bureau of Animal
Industry, and his assistants, in performing the autopsies recorded in
this report. I recommend the publication of the manuscript as
Bulletin No. 148 of the Bureau of Chemistry.
Respectfully,
H. W. WILEY, hil
Hon. JAMES WILSON,
Secretary of Agriculture.
2




THIS PUBLICATION may be pro-
cred from the Superintendent of
Documents, Government Printing Office
Washington, D. C., at 15 cents per copy













CONTENTS.


Page.
Introduction .................................... ..... .. .......... 5
rl review of the literature on the toxicity of caffein................ 9
Acute caffein intoxication .............................................. 18
Experi ts on rabbits............................................. 18
Subcutaneous injection ......................................... 18
Administration by mouth......................................... 26
Injection into the peritoneal cavity.............................. 28
Intra injection ............................................ 33
Intravenous injection............................................ 37
Summary........................ .......................... ..42
Expeiments on guinea pigs.......................................... 43
Subcutaneous injection........................................... 43
Injection into the peritoneal cavity................................. 47
Administration by mouth .. ................................ .. 49
Summary................................................... 52
Experiments on cats.............. ....... ......................... 53
Subcutaneous injection ......................................... 53
Iection into the peritoneal cavity............................. 56
Administration by mouth...... .... ... .... ...................... 57
Summary............................. ....................... . 59
Experiments on dogs .............. ................................ 60
Administration by mouth ........ ..... ....... .... ......... .......60
Subcutaneous injection ............. ..... ........... 60
Experiments on puppies .......................................... 61
Sum m ary ........................................................ 62
Chronic caffein intoxication ..... ............... .................... 63
Experiments on rabbits ................... .... ...... ....... ...... .. 63
Experiments on dogs ....... .... .............................. ...... 75

Ge e l su mary and conclusions ........ ............................ .. ., 95
Bibliography..... ..... ... .............. ..... ..... .... ... ..... ......... 97
3



















Digitized by the Internet Archive
in 2013













http://archive.org/details/spestcaffei00sala












THE TOXICITY OF CAFFEIN.


INTRODUCTION.

Comparative physiology has established the fundamental fact that
some properties are common to all forms of living matter. But the
same method of inquiry has also led to the recognition of marked
differences in the physiological processes of various species of animals.
Among the most important investigations which contributed to the
knowledge of such variation of function are the studies in comparative
metabolism. It is now recognized that metabolism is in some
respects quite different in herbivora and in carnivora. Some forms
of oxidaion are much greater in the rabbit than in cats and dogs.
Nuclein metabolism presents important differences in the rabbit and in
man, while the mode of neutralizing acid in the body may be cited as
another variation in the metabblism of these forms. Perhaps the
most striking examples of differences in the metabolism of different
organisms is furnished by the results of studies on the fate of certain
poisons introduced into the body.
The classical experiments of Bunge and Schmiedeberg a on the syn-
thesis of hippuric acid are of interest in this regard. It will be recalled
that in the dog the synthesis takes place in the kidney; the rabbit is able
to form hippuric acid in the liver as well as in the kidney, while frogs
can synthesize hippuric acid even when both of these orgas have been
removed or excluded from the circulation. Observations on the fate
of some of the alcohols of the fatty acid series have likewise shown that
these substances may be combined withglycuronic acid insome animals
but not in others. According to Thierfelder and Von Mering, ter-
tiary alcohols are combined in this manner in the rabbit but not in the
dog. According to Neubauer," the primary and secondary alcohols
are so combined in the dog as well as in the rabbit, but to a greater
degree in the latter.
Pohl 7 found that amyl alcohol is largely eliminated by the lungs in
the cat and in the dog. The proocols of his experiments show that
65 per cent of the alcohol given these animals was thus recovered,
while he recovered only 22 per cent of this substance in the expired
air of the rabbit. Examination of tne urine showed the presence of
glycuronic acid. HIofmeister's work with tellurium in the dog is of
a Th small gu refer to th bib graphy at the end of this bulleti.
5





6 THE TOXICITY OF CAFFEIN.

interest in this connection. He made the important discovery that
some animals possess the power of methylation as well as of demethyl-
ation. Abderhalden and Brahm's 1 experiments with pyridin show
that the same is true of young dogs when on a meat diet. is experi-
ments on rabbits with this substance were negative.
The metabolism of iaffein and theobromin furnish another illustra-
tion of differences in the physiological mechanism of animals. Al-
though the substances found in the urine of man, dog, and rabbit after
the administration of caffein and theobromin were the same, the quan-
tities varied considerably. According to Kruger and Schmidt," over
14 per cent of the theobromin introduced into the rabbit is eliminated
as 7-methyl xanthin in the urine. The dog eliminates only about 0.67
per cent. On the other hand, the amount of tri-methyl xanthin elimi-
nated was only 3 per cent in the dog and not quite 1 per cent in the
rabbit.
It appears, therefore, from studies in comparative metabolism,
whether endogenous or exogenous, that well-marked phyiologic and
chemical differences exist in various species of animals. That phar-
macological action may likewise vary in different species of animals
is shown by the following investigations. According to Guinard,"1
who made an exhaustive study of morphin, the reaction to tis alka-
loid varies in different forms of life, both qualitatively and quanti-
tatively. He established its narcotic effect in the dog, rabbit, guinea
pig, white mice, and rats, while for the cat, horse, ox, sheep, hog, and
goat it is, on the contrary, a stimulant. Moreover, there is no evi-
dence of cerebral effect. The stimulating effect of morphin on the
nervous system in some animals was also observed by Noe in experi-
ments with this substance on the hedgehog.
Guinard 28, 30 has also shown that morphin has no narcotic effect in
the marmot, although this animal is very sen.itive to the dr. Two
milligrams per kilo were found to be a surely fatal dose for this animal.
His experiments on the comparative toxicity of morphin 80 show a
)coniderable r range of variation in different species. Thus the fatal
dose for the dog was found to be 0.65 per kilo, while 7 mg per kilo is
the fatal dose for the horse. About twice the amount is fatal for the
ox and 0.2 mg per kilo kills the pig. Experiments with other drugs has
shown that a considerable range of variation in resistance exists in
animals of different species.
Noe's studies on the comparative toxicity of chloral brought out
the interesting fact that the rabbit is more resistant to it than the
hedgehog and the latter more resistant than the guinea pig. Per
haps the most striking example of a diference in reaction of the
same substance in widely different species is that furnished by
apocodei, quinnin, and yohimbin. According to Gunn, these sub-





INTRODUCTION. 7

,a have en found to cause vasodilation in warm-blooded
animals, but they constrict the blood vessels of the frog.
Experiments with apomorphin likewise show that the reaction to
this sutance varies in different species of animals. The resistance
of the cat to this drug is, according to Guinard,31 ten times greater than
that of the dog, and the latter is more sensitive than the rabbit to
the crystalline form of apomorphin when given intravenously.
According to Kobert4 amygdalin is without effect on dogs, but it
is poisonous to rabbits. Lapicque 4 found that the toxicity of
curara varies in different species of frogs, the dose required to pro-
duce paralysis in Rana esculenka being three times greater than in
Bufo vulgaris. Weir Mitchell pointed out long ago that turtles
stand enormous doses of curara. Schmiedeberg's experiments with
caffein on Rana temporaria and Rana esculeuta (and more recently
those of Jacobi and Golowinski 2 with caffein, theobromin, and
theophyllin) are also of interest in this connection. These experi-
menters observed well-marked differences of reaction to methyl-
xanthins in these closely allied forms.
Experiments with quinin have shown that the action of this sub-
stance differs in some animals. It causes a fall of temperature imme-
diately after its administration in the guinea pig, but frequently
produces, at first, a rise of temperature, followed by an unimportant
fa, in rabbits, dogs, and man.
he numerous investigations which have been carried out on the
effect of atoxyl within recent years have contributed much to the
comparative pharmacology of this substance. Although the symp-
tos and organic chanes produced by this substance in a variety of
animal present no great dfferences, the resistance of some ha been
found to vary; according to KSster 4 it is more toxic for dogs than
for rabbits. A number of other substances have been found by
various experimenters to vary in toxicity for different species of
animals. Cantharadin, phenol, atropin, and strychnin ay be men-
tioned as illustrations
Pharacological studies on lower forms of life have also revealed
marked variations in the effet of some poison. Observations made
by Danilewski with hydrochinone indicate that solution of 1 to
100 or 200 are toxic to Celentrates, causing paralysis in these oran-
isms. Echioder are killed within one or two hour in 1 to 1,0C0
or 2,000 solution, while in Vermes even weaker solutions cause
tetanus and finally paralysis. The experiments of Drzewina" with
potassium cyanid are also interesti in this connection. Teleosts
placed in 100 cc of sea water containing twentieth-normal potassium
cyaid showed signs of asphyxia and died in 10 to 20 minutes.
Actinia placed in a solution of sea water containing five times as
much potassium vanid were active on the thirteenth day of the





8 THE TOXICITY OF CAFFEIN.

experiment. Similar result were obtained with her e
organisms.
From these data it is evident that the toxicity of a sutance may
vary considerably in different forms of life. It has been shown also
by some investigations cited by Salant78 that the action of drugs
may be modified by different conditions in the environment as well
as in the subject of the experiment. The recognition of the import-
ance of these factors in determining pharmacological action has con-
tributed much to the elucidation of the mechanism by which drugs
and other substances produce physiological effects in the body. More
over, such knowledge has often enhanced the therapetic value of
pharmaco-dynamic agents and has frequently served to avert effects
of an undesirable character in man and domestic animals The results
obtained in one species of animals under a particular condition do not
admit, therefore, of universal application. Furthermore, the nature
of the action of a drug can only be partly learned from the manifes-
tation of its acute effects. Equally important, therefore, especially in
studies on toxicity, are the changes produced in chronic intoxication.
That the acute effects of a substance can hardly be considered a
correct estimate of its toxicity is shown by the evidence obtained in
experiments on tolerance and cumulative action of drugs; for the
toxicity of a substance may diminish when the substance is given
steadily for a long time if the body acquires tolerance for it. Arsenic,
morphin, and cannabis indica may be cited as illustrations of drugs,
the toxicity of which decreases with repeated doses, while digitalis
and lead show a tendency to increased toxicity when similarly
administered. Moreover the acute and chronic effects are sometimes
qualitatively different. According to Igersheimer"4 the symptoms
in acute atoxyl intoxication are nausea, vomiting, ad diarrhea.
These symptoms are absent in chronic intoxication, in whch trophic
disturbances of the skin and inflammation of the mucous membranes
were the effects produced. That the acute action of atoxyl differs
from the chronic effects was likewise shown by experiments o ani-
mals. The studies of von Anrep on chronic atropin intoxication
are of interest in this connection, as he found that after 10 to 15
injections of atropin there is no manifestation of symptoms such as
is observed in acute intoxication, while the effects on the circulation
are also less marked, the acceleration of the pulse being less than
after the sae dose in a normal subject not accustomed to its use.
When the administration of atropin is continued for a longer time
its usual effets on the pulse disappear altogether; there is, on the
contrary a decreased frequency of the pulse. If atropin has been
administered for from two o three weeks, respiration is likewise
affected.





HISTORICAL REVIEW. 9

ISORICAL REVIEW OF THE LITERATURE ON THE TOXICITY
OF CAFFEIN.

Caff was dicovered in 1820 by Runge," Pelletier," and Robi-
quet and was first analyzed by Dumas and Pelletier,20 but its
ect percentage composition was determined by Pfaff and Liebig,
7, l while to Herzog 3 *83 belongs the credit of having established
that it is basic. Strecker 82 prepared caffein synthetically by heating
theobromin silver and methyl iodid in a closed tube for 24 hours.
Soon after its discovery in coffee Oudry 67 reported the presence of
a substance in tea which he called "thein." Its identity with caffein
was established 15 years later by Jobst 4 and also by Mulder. 62, 83
According to Brill,13 Mulder (1838) was also the first to perform
experiments with caffein on animals. After the administration of
one-half grain to a pregnant rabbit he observed loss of appetite and
kyphosis. The rabbit aborted but recovered from the effects of
caffein. It has since been made the subject of numerous investiga-
tions which were carried out on a variety of animals. Observations
with caffein were also made on the human subject. About four
years after Mulder published his results, Lehmann 11 (1842) reported
experiments on a number of people who were given caffein. The
administration of from 2 to. 10 grains of the alkaloid was followed by
headache, palpitation of the heart, increased frequency and irregu-
larity of the pulse, tinnitus aurium, photopsia, insomnia, and even
delirium. Similar experiments reported by Frerichs 2 (1846) indi-
cate that in doses of 25 grains it may induce severe syptoms about
15 minutes after its administration. He also observed circulatory as
well as nervous symptoms and vomiting.
According to Albers 2 (1852), 4.5 grains of caffein citrate injected
subcutaneously into the thigh of a rabbit was soon followed by dimin-
ished motion and tremors of the operated thigh. Other symptoms
reported were spasms of the facial muscles, increased respiratory
movements, and mental confsion. Of interest in this connection
are the experiments of Cogwell7 (1852) on frogs. He concluded that
in point of destructive action on the tissues, cafein is far superior
to orphin and may be compared to strychnin and coniin, its action
on the nervous system he believed to be principally confined to the
fect on the brain and spinal cord.
Lehmann (1853) observed increased frequency of heart action
tr the administration of 4 grains, which were given with a normal
diet to an adult man. When the dose was doubled the frquency of
the pulse was still more increased, heart action became stronger, and
tremors and confusion of thought wth excitement of the imagination
made their appearance. There ws o an increased dere to
micturate.





10 THE TOXICITY OF AFFEIN

Stuhlmann and Falck 8 (1857) were the first to make a study of
the toxicity of caffin on animals of different species. The admini-
tration of 0.5 gram of caffein subcutaneously or per rectum in rabbits
induced tremors, tonic and clonic convulsions, paralysis, and inc ed
frequency of respiration at first followed by violent dyspna. On
autopsy he noticed congestion of the organs and in two of the three
rabbits experimented upon punctiform hemorrhages of the brain with
congestion of the meninges were found. In the other rabbit aemia
of the brain was observed. Experiments on cats were carried out
by subcutaneous, intravenous, and rectal injections. The sympto
observed after the administration of 0.5 to 0.7 gram of caffein were
the same as in rabbits except that the cats developed diarrhea when
caffein was given and no anatomic lesions were found on autopsy.
The effect of caffein on dogs indicated that in subjects of medium
weight a dose of 0.5 gram given by mouth might produce restlessness
and increased frequency of respiration, while the injection of the
same amount intravenously into such animals may cause death.
Large, full-grown dogs, however, survived an intravenous injection
of 2 grams of caffein, showing symptoms of incoordination, salivation,
and frequent defecation. These investigators also made observations
on caffein, using pigeons and other birds; 0.5 to 0.1 gram introduced
into the stomach caused vomiting, diarrhea, tonic, but more fre-
quently clonic, convulsions, incoordination, tremors, paresis, and
paralysis.
In a few, but not in all of the birds, there was at first increased
frequency of respiration followed by dyspnoea and circulatory dis-
turbances. These amounts of caffein proved fatal in all of the experi-
ments on birds. Inflammation of the intestinal mucosa and conges-
tion of the meninges were the only changes found on autopsy.
Stuhlmann and Falck also studied the effects of caffein on fishes and
toads. Mitscherlich 60 (1858) fed 0.4 gram of caffein with bread to a
rabbit and noticed lowered temperature, fatigue, convulsions, first
increased then decreased frequency of respiration, and on autopsy
congestion of all the viscera. He also reported observation on two
frogs, one of which was given one-sixteenth of a grain of caffein in a
pill with bread. It was administered to the other frog in aqueous
solution, but the mode of administration was not published. The
symptoms observed were in the main the same as in rabbits. In
pigeons 0.125 gram introduced into the stomach caused severe vomit-
ing, muscular incoordination, tonic rigidity of the limbs, and retrac-
tion of the head. Respiration was increased in frequency. Death
followed within 3 hours and 15 minutes.
From a series of experiments on frogs which Hoppe carried out
(185) by applying one-fourth of a grain of caffein to the muscles of
the back, he concluded that cein causes aralysis of the nees





HISTORICAL REVIEW. 11

Scord, and brain, sensation being paralyzed before movement.
hinjurious action of caffein proceeds, according to Hoppe, from
h spinal cord. This was based on experiments on two frogs, Rana
which the right leg was amputated, the nerve being left
intact, while the nerve of the other leg was ligated. At the end of
30 nutes paralysis was more marked on the right than on the left
side. In another frog of the same species he resected the femoral
nerv on the right side; about 1 hours after the administration of
caffein convulsions were observed. The left leg was rigid, but the
right was relaxed.
Voit (1860) ligated the vessels of the right lower extremity, cut
the nerves of the left leg, and introduced a few drops of caffein
solution into the stomach. Shortly afterwards tetanus of the right
leg occurred on touching the back of the animal; the left leg was
mtionless. Later the entire body exhibited tetanic convulsions.
From this and similar experiments Voit concluded that caffein acts
first and principally on the central nervous system, and that caffein
is also poisonous to nerve and muscle fibers, as they die when a solution
of caffein is applied to them. The action of caffein, according to
Voit, is similar in great part to that of strychnin. The effect on the
blood vessels is particularly interesting, as Voit observed dilatation
of the vessels, due as he thought to muscular paralysis, and also trans-
udation and congestion of the capillaries.
Kurzak (1860) made a study of the comparative toxicity of
caffein in frogs and rabbits and came to the conclusion that the lethal
dose for frogs is about one-seventh of that for rabbits. Caffein
citrate in the form of crystals was administered in both cases by
mouth. The doses given to frogs were 1 to 1.5 grains. He observed
convulsions and increased respiratory activity at first; after one hour
respiration diminished and voluntary muscular activity disappeared.
Even on the second day convulsions were sometimes noticed. Death
occurred at the end of the first or second day. Experiments on
only two rabbits were reported, 0.8 gram of caffein citrate causing
the death of one at the end of 13 hours. The symptoms noticed were
the sae practically as in frogs, but it is interesting to observe that
ecchymosis of the mucous membranes of the stomach near the cardia
was the only lesion found on autopsy. Several experiments made
on different days on the other rabbit indicated that the toxic
dose exceeded 0.5 gram, while smaller doses caused but very mild
symptoms.
According to Gentilhomme 0 (1867), after caffein the reflexes are at
first diminished and then disappear altogether. Death is produced
by stiffness and immobility of all the muscles, particularly of the
muscles of respiration, thus causing asph)yxi. He furthermore held
that caffein has no eect on cardiac or smooth mule fiber, its ac ion





12 THE TOXICITY OF CAFFEIN.

being specific on voluntary muscle fiber, contractions of which he
observed under the microscope, thus diffeing completely from strych-
nin, which is a nerve poison.
These observations seemed to be confirmed by Pratt 7 (1868), who
reported that the isolated posterior extremities and scle fibers of
the toad placed in a solution of caffein (1 grain to a wineglassful of
water) for three minutes were contracted, while controls placed in
distilled water were relaxed. This experiment is, of course, defective,
as normal salt solution should have been used in both cases. When
the muscular fibers previously immersed in caffein solution were
placed under the microscope violent contractions were observed.
The same author administered from 2 to 18 grains at a dose to five
healthy young men. After the administration of 12 grains he noticed
mental anguish, tremors of the hands and arms, and insomnia.
Doses under 5 grains had no marked effect except a diminution in the
frequency of the pulse and wakefulness.
About the same time Amory4 (1868) published the results of his
studies on the toxicity of caffein in cats, dogs, rabbits, and pigeons.
In all cases very large doses were introduced directly into the stomach
by means of a temporary gastric fistula. Ten grains given in meat
to a dog caused restlessness, but no other symptoms. Doses of 30
grains and above were invariably fatal. Seventy-three gains given
to a cat caused death within 20 minutes.
From observations on frogs, guinea pigs, rabbits, and on one dog,
Leven 53 (1868) concluded that caffein which he gave in the form of
the citrate in doses of 10 mg to frogs, from 150 to 200 mg to guinea
pigs, and three to four times the latter amount to rabbits, stimulates
the central nervous system and the voluntary, cardiac, and smooth
muscles. He found that 0.9 gram caffein was fatal for a rabbit when
injected subcutaneously, while 1 gram of the citrate was not toxic
for a dog of medium size. Caffein applied directly to muscle fiber
causes tetanus and destroys muscular contractility, while a nerve
fiber similarly treated loses its irritability.
According to Johansen (1869), calfein acts directly on the mus-
cular fiber. After the subcutaneous injection of 0.02 gram of caffein
into frogs, he observed contraction of the muscles at the site of injec-
tion, then contraction of the anterior extremities, and finally the
posterior extremities become rigid and extended. Johansen observed
muscular rigidity after cafl'in, even after curara was injected, or after
ligating the vessels, or cutting the nerves which supply the muscles.
He alo observed that large doses of caffein diminish muscular irita
bility. When cardiac muscle was poisoned with caffein, microscopical
examination showed that the striations disappeared. Johansen also
states that reflexes disappear after caffein poisoning. He never
observed tetanus in fros, but reorted tonic and clonic convulsions s





HISTORICAL, REVIEW. 13

a t of caffein poisonin in mammals. Somewhat different effects
of caffein in frogs were observed by Buchheim and Eisenmenger 1
(1870). After the injection of 2 per cent of the citrate the frogs soon
inactive. He also observed muscular twitching of the
extremities, which gradually increased, with rigidity of the muscles
opisthotonos, while respiration became slow and superficial,
fi y stopping altogether.
Aubert (1872) studied the toxicity of caffein in man and other
animals. After the ingestion of 0.36 gram, he observed dizziness,
but des of 0.12 and 0.24 gram were without any apparent effect.
On the other hand, a dose of 0.5 gram of caffein was followed by
increased frequency of the pulse, which soon disappeared. After one
hour he noticed dizziness and trembling of the hands, which likewise
pasd away soon. The injection of 0.16 gram of a 2 per cent solution
of caffein into the jugular vein of a rabbit weighing 1,090 grams
caused tetanus and death in two and one-half minutes, and 0.12 gram
injected into a rabbit weighing 980 grams caused death in one minute.
Much larger doses could be borne, however, when artificial respiration
was resorted to. A dog which was given 3 grams of caffein survived
when artificial respiration was performed. Aubert reports, on the
other hand, a similar experiment with 0.25 gram of caffein which
terminated fatally.
That caffein may give rise to different effects in various species of
animals was observed for the first time by Bennett.) He studied its
action on frogs, mice, rabbits, and cats, and attempted to determine
the minimum fatal dose in rabbits and cats. He also reported experi-
ments-with thein. In his first communication on the subject he
states that the administration of thein to rabbits first increased and
then diminished the frequency of respiration, while the pulse was
decreased in frequency. Caffein, which he apparently thought was
different from thein, caused increased frequency of respiration, while
the pulse was markedly retarded after a preliminary acceleration.
He also noticed congestion of the ears, muscular incoordination,
tetanus, paralysis, diminished reflexes, and contraction of the pupils.
Bennett reported the minimum fatal dose of caffein for a rabbit weigh-
ing 3.25 pounds as being 5.25-5.5 gains. The symptos in cats
after the administration of toxic doses of thein or of cafein er
groat excitement, paralysis alternating with convulsions, and profuse
salivation. T'he minimu fatd dlose for a cat weghin 5 pounds
ws, according to Bennett, 6 rans of caffein and 5.5 rains of thein.
ly one experient on a mous is reported; the administration of
0.1 grain proved fatal. The symptoms were the same as those
observed i cats and rabbit after the administration of caffein. The
xperiments on frogs indicate that the symptoms were about the
same s those viously described in the case of warm-blooded ai-





14 THE TOXICITY OF CAFFEIN.

mals except that the reflexes are almost completely lost the sub-
cutaneous-injection of doses of one-sixteenth to one-twelfth of a grain.
The latter dose was fatal for frogs. It would be of inte t to know
the comparative toxicity of caffein to frogs and mamm
tunately the weights were not reported.
Schmiedeberg (1874) noticed that the adinistration of 20 mg of
caffein to frogs weighing about 45 grams was followed, in Rana esc-
lenta, in about 25 minutes, by increased reflexes, 7 minutes ter
by tetanus. Several attacks occurred, but tonic spasms were never
observed. On the contrary, when the same amount of caffein was
given to Ranc temporari weighing 45 grams he noticed a marked
diminution of the reflexes and tonic rigidity of the musles after 23
minutes; the reflexes were greatly increased, however, about 24 hours
later. The frogs were under observation for three days, and although
symptoms were still present at the end of this time in the subjects of
both species tetanus was never observed in Ran temporaria.
Peretti's 70 (1875) studies on the effects of caffein were confined
chiefly to observations on dogs. He also made observations on a
few rabbits and reported an experiment on one cat to which he admin-
istered, by subcutaneous injection, 0.18 gram of caffein per kilo and
noticed increased frequency in lachrymation and crying. The cat
was found dead the next day. The subcutaneous injection of a rabbit
in which artificial respiration was instituted with 0.36 gram of caffein
per kilo proved fatal soon after the injection without any manifesta-
tion of symptoms. Small doses of caffein, 0.1 gram, given to a rabbit
weighing 3,670 grams, failed to produce any visible effects. Doses
under 0.1 gram per kilo likewise failed to induce any symptoms in
dogs. When 0.1 gram of caffein per kilo was given by outh or sub-
cutaneously it was followed by restlessness, salivation, rigidity o
hind legs, and vomiting. In both instances the dogs recovered The
symptoms were more severe when the dose was increased to 0.185
gram per kilo, but even in this case the dog recovered. A dose of 0.2
gram per kilo, however, proved fatal.
Henneguy "1 (1875) experimented on three frogs to which he gave
0.01 gram of caffein citrate subcutaneously. He observed mild stim-
ulation of the nervous system and of the muscles, as well as increased
cardiac activity. Later, voluntary movement and respiration disap-
peared and sensations diminished, but convulsions of the extremities
appeared. Cardiac activity was ther diminished, the heart being
finally arrested in systole. Since the motr nerves retained their irri-
tability even after the reflexes disappeared, he cocluded that the
los of motion wa due to the action of caffein on the nerve center
Binz 1 (1878) reported experiments on dogs and also made some
observations on man with caffein. The subcutaneous injections of
0.2 gram caffein may prove fatal to dogs, although some survive such






HISTOICA REVIEW. 15

The toxic dose in man varies from 0.5 to 1.5 grams. Dis-
trance of the circulation, such as palpitation of the heart and full-
of pulse, restlessness, and diarrhea were the symptoms he
observed.
Extensive investigation on the action of caffein were carried out
y Leblond (1883), who studied its effect on the circulation in man
wer animals, and its toxicity in the lower animals alone. Five
to twenty centigrams of caffein and 0.06 to 0.25 gram of salicylate of
soda were dissolved and injected into the muscles of the thigh of
young guinea pigs weighing a little over 300 grams. In the three.
p ents reported the death of the animals occurred after 23 min-
utes, 40 minutes, and 1 hour and 20 minutes. Symptoms appeared
in from 10 to 15 minutes after the injection of caffein. Incoordination
of movements, convulsions, both tonic and clonic, opisthotonos,
tremors increased frequency of respiration, ataxia, paralysis were
the symptoms observed. It is worthy of note that the appearance
of paresis preceded the convulsions. Diminished sensation was
reported in one pig, but no sensory disturbances nor reflexes had been
observed in the other. Two rabbits, one of which received 0.5 and
the other about 0.3 gram of caffein per kilo with equal parts of sali-
ylate of soda, were injected subcutaneously into the thigh. Dimin-
shed sensation, paresis of the posterior extremities, hyperexcita-
bility, nvulsions, opisthotonos, dilation of the veins of the ear were
observed. Death followed in 1 hour and 23 minutes in one rabbit
and in 3 hours and 7 minutes in the other.
Filehne (1886) experimented with caffein on Rana esculenta and
Rana temporaria. The subcutaneous injection of 7 mg of caffein into
Raia esclenta caused tetanus, while 50 mg given by mouth caused
tonic spasms. He further stated that the difference between Rana
a and Rana te poraria as regards the reaction to caffein was
one of degre only.
Amat (1889) reported experiments on three guinea pigs, in which
0.4 to 0.5 gam per kilo injected subcutaneously proved fatal wthin
38 and 44 minutes. One guinea pig which received 0.1 gram of
caffein per kilo survived. The symptoms observed in the two fatal
cases were general muscular rigidity and convulsions.
Parisot (1890) made a study of the toxicity of caffein on different
species of anials. Unlike most of his predecessors, however, he
reported, at least in some cases, the weight of the anials on which he
worked. After the subcutaneoum and intramuscular injections of
from 5 to 20 mg of caffein into aa teporaria weighin from 14 to 16
rams, he noticed increased irritability at first; later, a loss of reflexes,
inability to use the muscles, omplete uscular riidity resembli
rigor mortis, ad also cessation of heart action. The effect of calfein
produd in the green frog was analous to that obsered in






16 THE TOXICITY OF CAFFEIN.

strychnin poisoning. Parisot found, however, that muscular rigidity
developed, although very gradually, alo in the green frog, but it set
in much later than in frogs of the other species and without super-
seding the clonic convulsions. According to Parisot, the muscular
rigidity after caffein persists after the destruction of the brain and
spinal cord, thus showing that it is not of nervous origin. He further
emphasized the difference in the behavior of these two species of frogs
toward caffein by stating that he never observed tetanic convulsions
in the red frog. His experiments also indicate that the green frog is
more resistant to caffein than Rana temporaria, as the same doses
which are fatal for the latter were only toxic for Raa e lea.
The number of experiments, however, is too few to justify a positive
conclusion on this point. Parisot also made some experimens on
turtles. The results he obtained show that caffein is at least as toxic
for these animals as for the frogs he experimented upon, 0.33 gram
per kilo (carapace not included in weight) having proved fatal within
24 hours. Two experiments on one pigeon were also reported by the
same observer; two doses of 0.06 gram per kilo given at an interval
of four hours caused mental depression and muscular rigidity, but the
pigeon survived.
Experiments with caffein on the human subject made by Parisot
showed that man is far more susceptible to this substance than the
other animals he investigated. After the ingestion of 0.3 gram of
caffein symptoms of intoxication pointing to cerebral disturbance
appeared, which became more marked when the size of the doses was
increased.
It will be noticed that the nature of the action of caffein, whether it
is a nerve or a muscle poison, formed the subject of several investiga-
tions. Binz 11 (1890) brought forward additional evidence in support
of the view that caffein acts primarily on the ganglion cells, and not on
the muscle directly. This he has shown by injecting 0.5 gra into
each of two rabbits after cutting the sciatic nerve on one side; n one
cas he also resected the obdurator and crural nerves on the same side
('lonic spasms developed in both subjects soon after caffein was given,
but in each rabbit the side operated upon remained pralyzed.
Baldi 8 (1891) studied the action of caffein on Rana ea. After
injecting from 4 to 20 mg tetanus, such as observed in strycnin
poisornig, was noticed. Fr6hner (1892) made observations on the
comparative toxicity of cafin in domesticated animals. After the
administration of 5 grams of caffein sodiumsalicylate by mouth to a
dog weighig 10 kilos, he noticed salivation, restlessness, vomiting,
and convulsions as in strychnin poisoning. Death occurred three
hour after the drug wasgiven. On autopsy he noticed mid infamm-
tion of the mucos embraes of the stomach and intestines and
edema of the lungs; the heart was in diastole. A dose of 2 grams of





HISTORICAL REVIEW. 17

sodium salicylate given to the same animal subcutaneously two
days previously provoked only very slight symptoms. The sub-
cutaneous injection of 10 grams of the same preparation into a pig
weighing 30 kilos caused death in two and a half hours, with the pro-
duction of symptoms of disturbance of the nervous system and of
strointestinal irritation. The same dose per kilo of body weight
given to a goat likewise caused death in two and a half hours after its
administration. Examination on autopsy revealed inflammation of
the gastrointestinal tract. Similar lesions were found in a horse
killed by 100 grams of caffein, in which he also noticed hemorrhage
of the mucosa in the fundus of the stomach.
Gourewitch (1907) conducted experiments with caffein on
rabbits, pigeons, and white rats. It appears from his protocol that
single doses of about 0.2 to 0.25 gram caffein per kilo given subcuta-
neously proved to be fatal. He states, however, that the resistance
Sto cwas markedly diminished, when its administration was
repeated daily, for much smaller amounts sufficed to cause death in
these animals. A dose of 120 mg of caffein per kilo proved fatal after
the third injection. When the dose was increased to 170 mg per kilo,
the animal succumbed to the effects of caffein after the second injec-
tion. His experiments on the other animals do not indicate the
degree of resistance to caffein, since the weights for some were not
given while for the others no attempt was made to determine the
inimum toxic or fatal dose.
Maurel 1 (1907) studied the influence of different methods of
administration on the toxicity of caffein on frogs and rabbits. He
determined the mnimum toxic and lethal doses of caffein hydro-
bromid which he employed in 1 to 2 per cent solutions. He concluded
from his experiments that the toxicity of caffein when given by
muth is twice as great for the frog as for tha rabbit.
More recently Hale carried out a number of experiments on guinea
pigs in which he determined the toxicity of caffein given in the form
of the citrate and made into a pill with mucilage of acacia and arrow-
root starch. After the pill was dried it wa fed to the animal, due
precaution being taken that none of it was lost during feeding.
From experiments on ginea pigs which received doses (f 0.3 to 0.6
gram caffein citrate, the following data have been reported: Three
decigrams per kilo given to one pig was not fatal. Of three pis
which received 0.4 per kilo, one died and two survived. Exactly
the same reult were obtained in three others which received 0.5 per
kilo. Two guinea pigs, which received 0.55 and 0.6 per kilo each,
died aft 15 and 7 hou, respectively, while another animal survived
a dose of 0.45 per kilo.
185-Bu. 14-12-2






18 THE TOXICIT OF CAFFEIN

This review of the literature on the toxicity of caffein, alough
bearing evidence of considerable investigation and ext g over
three-quarters of a century, is largely quaitative in character. It
appears from the experiments that the main object of the investiga-
tions was to ascertain the nature of the action of caffein, whether it
is a muscle or a nerve poison. The comparative toxicity in different
species of animals by the accurate determination of the toxic and
fatal doses received but little attention. To fill the gap in our
knowledge of the toxic effects of caffein, the present investigation
was undertaken. This, it will be seen, proved to be a most laborious
task, because in the large number of experiments careful observations
showed that individuals of the same species varied considerably in
their reaction to the drug. Numerous other factors, as will be shown,
were also found to play an important part in the determination of the
toxicity of caffein.

ACUTE CAFFEIN INTOXICATION.

The object of these experiments was to determine the resistance
to caffein in various species of animals and by various methods of
administration. Caffein was therefore given by mouth and inected
subcutaneously into the peritoneal cavity, into the muscle, and in-
travenously. As far as could be judged by appearance, healthy ani-
mals were selected for the subjects of the experiments, but as it is
impossible to diagnose with any degree of accuracy the condition of
the animal while it is alive, post mortem examinations were resorted
to in many cases in which the issue of the experiment was fatal.
Since the age of the animal may modify toxicity full grown, as well
as young, animals were employed for these experiments; diet, race,
and season also play an important part in determining the toxicity
of a drug and these factors were also taken into account in the present
investigation.
EXPERIMENTS ON RABBITS.

Animals of different varieties were used and were given caffein by all of themethods
indicated in the preceding paragraph. Some of the rabbs employed in these experi-
ments received oats, others receivd a diet exclusively of carrots forseveral daysorweeks
previous to the administration of caffein. The experiments were conducted at all sea-
ons of the year.
SUBCUTAINEOUS INJECTION.
From a study of the literature on th ttoxicity of caffein it seemed hatabout 150 mg
per kilo is probably the lethal dose for the bbit when the drug is injected subcuta
neously. rliminary observations were therefore carried out with such a doe, but
it wa found, on the contrary, that th aount per kilo was hardly ufficient induce
symptoms in the reat mority of cases.






ACUTE INTOXICATION-BABBITS. 19

SERIEs A.
[Dose of 147 to 167 mg of caffein per kilo were employed n these experiments.]
Rabbit 2. Belgian hare, female. Weight, 1,070 grams. Diet, oats.
March 25: 8.5 cc 2 per cent caffein (158 mg per kilo) injected subcutaneously at
2.15 p. m.; 4 p. m., reflexes increased; 5.45 p. m., increases of reflexes still more
marked.
March 26: Rabbit looked normal; no symptoms observed.
Rabbit 331. Belgian hare, female. Weight, 1,170 grams. Diet, oats.
March 25: 2.15 p. m., 9 cc 2 per cent caffein (153 mg per kilo) injected subcutane-
ously; 4 p. m., reflexes increased; 5.45 p. m., condition the same.
March 26: Rabbit looks normal; no symptoms observed.
Rabbit 328. Belgian hare, female. Weight, 1,200 grams. Diet, oats.
March 25: 9 cc 2 per cent eaffein injected subcutaneously (150 mg per kilo); 4 p. m.,
reflexes increased; 5.45 p. m., reflexes increased but not markedly.
March 26: No symptoms; rabbit looks normal.
Rabbit 322. White female. Weight, 1,065 grams. Diet, oats.
March 17: 8 cc 2 per cent caffein (150 mg per kilo) injected subcutaneously at 11.55
a. m.; 12.55 p. m., reflexes increased, but no tetanus nor any other symptoms.
March 18: Rabbit running around in cage; condition apparently normal.
March 25: Condition of rabbit good.
Rabbit 217. White. Weight, 1,355 grams. Diet, oats.
October 29: 10 cc 2 per cent caffein (147 mg per kilo) injected subcutaneously at
1.51 p. m. 5.15 p. m., rabbit alive; survived.
Rabbit 219. Maltese. Weight, 1,820 grams. Diet, oats.
October 29: 14 cc 2 per cent caffein injected subcutaneously at 1.40 p. m. (153 mg
per kilo); 5.15, rabbit alive; survived.
Rabbit 194. White female. Weight, 1,490 grams. Diet, oats.
October 14: 13 cc 2 per cent caffein (174 mg per kilo) injected subcutaneously;
increased reflexes and tremors were observed.
October 15: Condition of rabbit good; no symptoms.
Rabbit 191. Brown male. Weight, 1,915 grams. Diet, oats.
October 14: 16 cc 2 per cent caffein (167 mg per kilo) injected subcutaneously;
reflexes increased and tremors present.
October 15: Condition of rabbit good.
A study of this seris shows that about 150 mg of caffein per kilo caused increaed
reflexes within one to two hours after injection. When the dose wa increased as
in rabbits 194 and 191, the symptoms were more pronounced; 150 mg per kilo may
be regarded as the minimum dose which produces symptoms of nervous irritability
when caffein is injected subcutaneously. Experiments with larer doses were there-
fore carried out in order to determine the minimum fatal dose.

SERIES B.

Approximately 0.2 gr of caffein per kilo was employed in those experiments.
Diet and ra a possible factors which may influence the toxicity of caffein were
made the subject of study in these experiments which were divided into two grous
as shown in the ble, page 25.
Rabbit 95. Gray and whte ale. eit, 1,478 grams. Ditt, oats.
February 27: 11.30 a. m., 15 cc 2 per cent cffein (210 mg per kilo) injected sub-
cutaneously; 2.20 in., no sympt4 is, tremors observed when handled, but not
marked, reflex slightly increasd, no mu lar riidity nor any other symptoms;
2.45 p. m., rabbit suddenly became very restles, jumped off the tble, and had
convulsions; 3.45 p. m., rabbit died, rigor mortis set in almost immediately after
death.
Rabit 96. Gray and white male. Weight, 1,585 grams. Diet, oats.
February 27: 1 2 per cent caffein (20 mg per kil) injected subcutaneo~ ly
at 3.40 p. nm.; increased reexes observed aut one hour after caffein was injec
but no other syi)tome.
February 28: abbit found dead.
Rabbit 11!. BleSk female. Weight, 75 rams. Diet, oats.
March 18: 9 cc 2 per cent caffein (2 g per kil) injected subutaneously at
3 p. in.; 3.30 p. m., rabbit became restess reflexes were increased, tremors were






20 THE TOXICITY OF CAFFEIN.

observed, but no other symptms; 4.15 p. m., rabbit had tremors, was d but
this failed to induce tetanus, 10 minutes later tetanus of short duration
occurred.
March 19: 9 a. m., found dead.
Rabbit 119. Yellow white female. Weight, 1,060 grams. Diet, oats.
April 17: 10 cc 2 per cent caffein (188 mg per kilo) injected subcutaneoly at
2.10 p. m.
April 18: Rabbit found dead.
Rabbit 195. White female. Weight, 130 grams. Diet, carrots, October 7.
October 14: 13 cc 2 per cent caffein (0.2 gram per kilo) injected subcutaneously at
11.15 a. m.; 2.25 p. m., rabbit had convulsions and died. e: Ulceration of
rectum was noticed.
Rabbit 208. Gray. Weight, 1,068 grams. Diet, carrots, October 7-15, iclusi
October 15: 10 cc 2 per cent caffein injected subcutaneously at 11 a. m.; 1 p. m.,
increased reflexes and tremors observed; 3.45 p. ., tremors were marked when
rabbit was handled.
October 16: Rabbit found dead. Note: Looked poorly nourished.
Rabbit 247. Belgian hare, female. Weight, 1,295 grams. Diet, oat ast 10 day before
experiment.
November 10: 11 a. m., urine obtained from the bladder was acid to litmus and
did not contain sugar or albumen, 13 cc 2 per cent caffein was injected subcutaneously;
1.30 p. m., 15 cc urine obtained was markedly alkaline to litmus and reduced Feh-
ling's solution; 2.30 p. m., reduction of urine considerable, marked tremors observed
but no tetanus.
November 11: 10.30 a. m., 95 cc urine collected gave moderate reduction of Feh-
ling's solution, no symptoms, condition of rabbit seemed to be good.
Rabbit 248. Belgian hare, female. Weight, 1,305 grams. Diet, oats the last 10 days
before the experiment.
November 10: 11 a. m., urine markedly acid to litmus, no albumen, no s r;
13 cc 2 per cent caffein injected subcutaneously; 1.30 p. m., urine wa slightly alka-
line to litmus, no reduction of Fehling's solution; 2 p. m., reflexes increased; 2.30
p. m., 2 cc urine obtained from bladder, sugar abundant; 4.45 p. ., reflexes in-
creased as before, but no tetanus.
November 11: 10.30 a. m., urine collected showed slight reducion of F ling's
solution; otherwise condition of rabbit was good; rabbit did not any effects
of caffein.
Rabbit 7. Belgian hare. Weight, 1,040 grams. Diet, carrot, March 1 to April 6,
inclusive.
April 6: 3 p. m., 11 cc 2 per cent caffein injected subcutaneouly in the back
(0.211 per kilo); 4.30 p. m., reflexe much exaggerated.
April 7: 8.15 a. m.; condition good, no symptoms.
Rabbit 336. Belgian hare Wight, 1,040 grams. Diet, carrots, March to April 6,
inclusive.
April 6: 3 p. m., 11 cc 2 per cent caffein injected subcutaneously into tissues of
the back.
April 7: 8.15 a. m., no symptoms, condition good.
Although symptms appeared in rabbits of Group I (see table, pa 2) abut th
sae time after the administration of caffein as in the rabbits of the preceding series
all of them terminated fatally 2t hours to 24 hou after its administration. Two
of these rabbits (Nos. 195 and 208) were fed carrots for several days before the injec-
tion of caffein, the others were fed oats. Since symptoms and death appeared in
these two rabbits about the same time as in the rest of this group it may be concluded
that eaffein is not less toxic when car)ts are fed than when ts form the exclu
diet. But since rabbit No. 208 was poorly nourished and ulceration of the rectum
was observed in No. 195 it is quite possible that affein might be les toxic in
normal rabbits on this diet. This was tested in rabbit No. 336 and 337, both of
which seemed to be free fro abnormality d were well nourished. Sinc these
rabbits survived and manifested mild sypto only of intoxication it would seem
that a carrot diet decreasthe toxicity of caffein.
It was sugested, however, that another factor might be the cae th greater
reistace to caffein in thee wo rabbits, naely, race. This was tested in rabbit 247
and 248, both Beian hare. Since the toxicity of caffein in these two abbits was the






ACUTE INTOXICATION-RABBITS. 21

ame as in Nos. 336 and 337, diet as a factor in acute caffein intoxication may be dis-
ed. The greater resistance to caffein of these four rabbits is in all probability
due, therefore, to a difference of race. This suggestion gained additional support
from e experiments of the next series.

SERIES (C.

The object of these experiments was to determine the minimum fatal dose for the
gray rabbit and to obtain additional evidence as to the toxicity of caffein in the several
varieties of rabbits. Eight experiments were performed, in which from 236 to 252 mg
per kilo were given. The white rabbits, three in number, received 250, 242, and 238
Ing perkilo. All the others (which were Belgian hares) received from 236 to 252 mg
per kilo. Two of the white rabbits were fed carrots for one week preceding the injec-
tion of caffein. The other was fed oats. Three of the Belgian hares were on a diet
of oats, two were fed carrots the week before the experiment with caffein.
Rabbit 1. White,female. Weight, 2,060 grams. Diet, oats.
April 14: 25 cc of 2 per cent caffein (250 mg per kilo) in aqueous solution injected
subcutaneously in the back at 1.35 p. m.; 4.30 p. m., tremors, reflexes increased,
condition otherwise good.
April 16: 9 a. m., found dead in cage. Autopsy: Liver deeply congested; kidneys
congested in cortex and medulla; stomach showed small hemorrhagic areas, perforating
ulers in pyloric portion; small intestine petechiated on mucosa; lungs and spleen
normal.
Rabbit 4. White, feale. Weight, 1,650 grams. Diet, November 2-9, carrots.
November 9: 10.45 a. m., 20 cc 2 per cent caffein (242 mg per kilo) administered
subcutaneously.
November 10: 9 p. m., found dead.
Rabbit 35. Gray hare, female. Weight, 1,170 grams. Diet, March 31 to April 7,
carrots.
April 7: 9.30 a. m., 14 cc 2 per cent caffein solution (240 mg per kilo) injected sub-
cutaneously in the back; 10.30, reflexes much increased, rabbit is extremely sensitive.
April 8: 9 a. m., found dead. Autopsy: Liver was congested and contained several
coccidiosis nodules; stomach distended with rather dry food mass; ucosa exhibited
d catarrhal inflammation; mucosa of intestines al slightly inflamed.
Rabbit 49. Belgian hare, female. Weight, 1,185 grams. Diet, oats.
November 11: Urine, 5 cc, from bladder acid to litmus, no sugar, no albuin; 11.50
a. m., 14 cc 2 per cent caffein (236 mg per kilo) administered subcutaneously; 3.45
p. n., reflexes increased, hypertheia marked, but no tenus, even when handled;
0 cc urine collected at 4 p. m., reduction of Fehling's solution considerable.
November 12: 10 a. m., 8 cc urine collected, reduction heavy, only a few cubic
centimeters otained from bladder, did not contain any sugar, general conditio of
rabbit good, no symptom of caffein intoxication.
Rabbit 32. Yello, female. ight, 1,135 grams. Dit, oats.
March 16, 1910: 11.50 a. m., 14 cc 2 per cent caffein (246 mg per kilo) injected sub-
cutaneously in the ack; 2 p. m., reflexes increased, very sensitive, s ed to run
when put on floor, no hadling except what was require for removal and retur to
cag, eces soft.
March 17: 9.30 a. ., condition good, bit put on floor, gait normal, but does not
care to walk.
March 18: 9 a. i., walks around when put on floor, appetite good, condition seems
to be normal.
March 25: 11 a. m., rabbit still alive, condition good.
Rabbit 250. Belgian hare, fem ght, 1,45 grams. Dit, ots at ast two days
before the experiment.
November 11: 11 a. n., urine obtained from bladder acid to litmus, no albumin
no sgar; 11.10 a. m.a 18cc, 2 per cent caffein (252 mg per kilo); 3,45p. m.1 reflexes and
eiano tetanus; 4p. m., 60 urine, mrked reduction of ~bling's slution.
November 12: 10 a. m., conition of rabbit go, no symptoms ofcaffein intoxicat on
80 c urine collecte u consdrable, only a few cubi centietes of uine obtaine
from bldder, no reducon of hli's solution.






22 THE TOXICITY OF CAFFEIN.

Rabbit 334. Belgian hare, female. Weight, 1,70 grams. Diet, carrot, March 1to
April 7.
April 7: 9.30 a. m., 15 cc 2 per cent caffein (240 mg per kilo) inj subutane-
osly in the back; 10.30 a. m., reflexes much increased, rabbit extre ly sensitive.
April 8: 9 a. m., condition good, no symptoms.
Rabbit 33. White, male. Weight, 1,675 grams. Diet, arrots, November to 9.
November 9:10.50 a. m., 20 cc 2 per cent caffein (238 mg per kilo) incted subcuta-
neously, no symptoms observed until 5 p. m., when increased reflexes and h
sia were noticed, but no tetanus.
November 10: 9 a. m., paralysis of posterior extremities; died at 1 p. m.
Analysis of the results obtained in the experiments of this series and inspection of
Table I, page 25, show that all four of the rabbits which survived doses of 236 to 252 mg
of caffein per kilo were Belgian hares. Of the four which died one only was a Belgian
hare. The other three were white rabbits. Two of these were fed oat; the other two
received carrots during seven days preceding the administration of caffein. Thisdiet
does not seem to be a factor, therefore, in the toxicity of caffein. Moreover, it may
be observed that rabbit No. 122, which was fed oats, died after receiving 250 mg per
kilo, while rabbit No. 250 received the same diet and survived the same dose of caffein
per kilo.
Experiments 234 and 334 offer another illustration that the toxicity of caffein is not
dependent upon diet, since both rabbits were fed carrots, but the same dose of caffein
caused only symptoms in one while it proved fatal to the other. It is evident, there-
fore, that the difference in resistance to caffein shown in these experiments is in all
probability due to race, the Belgian hare being more resistant to caffein than rabbits
of other varieties. Rabbit No. 335 seems to be an exception, but the post-mortem
examination showed the presence of coccidiosis of the liver. As will be shown later,
wherever this condition prevailed even smaller doses of caffein proved fatal.

SERIES D.

To obtain additional evidence regarding the resistance of the various races of rabbit
to caffein and to ascertain the smallest dose which is surely fatal to the gray rabbit or
Belgian hare was the object of this series of experiments. The diet in all case con-
sisted of oats, which was given ad libitum excepting to rabbit No. 235, which received
carrots for one week previous to the injection of caffein. The doses administered
ranged from 267 to 300 mg per kilo and were administered to different varities of adult
rabbits.
Rabbit 253. Brown and black, male. Weight, 1,600 grams. Diet, oats, Noember9 to 12.
November 12: 11.30 a. m., urine from bladder acid, no albumen, no sugar; 11.35
a. m., 22 cc 2 per cent caffein (275 mg per kilo) injected subcutaneously; 11.45 a. .,
rabbit jumped off the table, had convulsions, retraction of heaad oithtonos,
general tremors, anterior extremities stretched out, posterior extremties almost
normal, frequent twitchings; died at 12.15 p. m.
Rabbit 252. Black, feale. Weight, 1,335 grams. Diet, oats, November 9 to 12.
November 12: 11.30 a. m., 18 cc 2 per cent caffein (270 mg pr kilo) injected
subcutaneously. Urine obtained from bladder before injection, acid, no albmen,
no sugar, color noral, tremors and great excitement noticed about 12 noo; 4.30
p. m., when handle, showed nusal restlessness and excitement followed by con-
vulsions with opisthtonlos; occasional twitching, condition ba. Die 4.3 p. m.
Rabbit 7. White, female. eight, 80 grams. Diet, oats, March 8 to 16.
March 16: 11.45 a. m., 12 cc 2 per cent caffein (292 mg per kilo) injected sub-
taneously in the back; 2 p. m., found dead, but was still warm. A op: emor-
rhagic area at point of ijection into spial muscles; ubctaneous abdominal region
exhibited a lare area of cheesy prulent material; liver and spleen were engorged;
bladder filled; intestines normal.
Rabbit 340. White and browin male. Wight, 1,465 grams. Diet, oats.
March 30: 3.20 p. m., 20 cc of 2 per cent caffein (273 g per kilo) injected sbu-
tneously in back.
March 31: 9 a. m., found ead.






ACUTE INTOXICATION-RABBITS. 23

Ra t 41. White and brown. Weight, 1,450grams. Diet, oats
March 30: 3.20 p. m., 20 cc 2 per cent caffein (270 per kilo) injected subcu-
St ouly in back; 4.40 p. m., found in dying condition, had convulsions; 4.45 p. m.,
dead.
Rabbit 326. White, male. Weight, 1,645 grams. Diet, oats, March 8 to 16.
March 16, 1910: 12 noon, 20 cc 2 per cent caffein (243 mg per kilo) injected subcu
taneously in the back; 2 p. m., tremors marked, hypersensitive, started to run when
put on floor; rabbit was not handled any more than was required for his removal from
and return to cage.
March 17: 9.30 a. m., tremors still present and marked, otherwise general condition
good; no other symptoms.
March 18: 9.30 a. m., no appetite, tremors still present, general condition poor;
died about 2 p. m.
Rabbit 35. Belgian hare, male. Weight, 1,870 grams. Diet, carrots, November 2 to 9.
November 10: 11.05 a. m., 25 cc 2 per cent caffein (267 mg per kilo) injected subcu-
taneously; reflexes increased and tremors, but no tetanus observed; found dead next
morning.
Rabbit 316. Belgian hare,female. Weight, 860 grams. Diet, oats, March 8 to 16.
March 16, 1910: 11.40 a. m., 12 cc 2 per cent caffein (267 mg per kilo) injected sub-
cutaneouly in the back; 2.15 p. m., reflexes somewhat increased, but not markedly
so; walked when put on floor; gait clumsy and slow; tremors of head observed; 2.35
p. ., rabbit lying in his cage, posterior extremities extended and rigid, anterior
extremities flexed, head retracted; is still breathing; occasional spass observed.
Rabbit died at 3 p. m. Autopsy: No lesion at point of injection in dorsal spinal
muscles; liver and spleen engorged; intestines injected; other organs apparently
normal.
Rabbit 395. Belgian hare, male. Weight, 1,410 grams.
August 18:1 p. m., 20 cc 2 per cent caffein (283 mg per kilo) injected subcutaneously
in the back; 4 p. m., reflexes markedly increased; 5 p. m., reflexes about the same,
but no tetanus.
August 19, 9.15 a. m.: Reflexes increased markedly.
August 21, weight, 1,215 grams. Given 275 mg per kilo of caffein; no symptoms
observed.
Auust 23, found dead. Autopsy: Liver greatly engorged; stomach fairly well dis-
tended and mucous membrane in a slightly inflammatory condition; contents of
sall intestine liquid in nature, but walls of same appeared normal; other organs
normal in appearance.
Rabbit 96. Belgian hare, female. Weight. 1,475 grams. Diet, oats.
August 18: 1p. m., 20 cc 2 per cent caffein (272 mg per kilo) injected subcutaneously
in the back; 4 p. m., reflexes increased markedly; 5 p. m., reflexes increased markedly
but no tetanus.
August 15: 10.30 a. m., reflexes still increased very markedly; rabbit jumps when
touched.
August 21: Weight, 1,245 grams. Injected subcutaneously 275 mg of caffein per
kilo; reflexes increased, posterior extremities stiff over hour later.
August 22: 9 a. m., found dead. Atopsy: Thoracic orans norml in appearance;
stomach distended and mucous membrane affecd with a calrhal inflanation;
contents of tomach were covered with a shiny mucus: contents of small intestine
liquid in nature and bile stained; liver showed a cccidial infestation; kidneys and
spleen normal in appearance.
Rabbit 397. Belgian hare, ale. Wght, 1,375 grams. Diet, oats.
August 19: 10.30 a. m., 20 cc 2 per cent caffein (290 g per kilo) ijected sbcu
taneously in the back.
August 22: 9 a. ., found dead. Autopsy: Stomach distended with inges;
mucous membrane exhibited a catarrhal influnination with excessive secretions;
major portion of inesties sh ed a condition smilar to that of stomach, cntents
consting mainly of a shiny mucus; livenlarged; other organs apparently normal.
Rabbit 8, Belian hare, fea. ight, 1,570 grm. Dit, oas.
August 19: 10.30 a. m., 23 cc 2 per cent caffein (293 mg per kilo) injectd ubcutane
ously in the back; 4 p. m., found dad. Autopsy: Thoracic organs seti no l;
mucos membrane of stomach exhibited catarrhal infla ation ge ally; lar
inte s mewhat impacted but walls apared n al; othr organs noral.
Rabbit 99, Belgian hare, male. Itght, 1,725 rams. Diet, oats.
August 19: .30. m., 26 cc 2 per cent caff e (300 mi per klbu e-
uslyin the back; foud dead at 4.30 p. m. Autoy: ngsslightly congested; liver

I






24 THE TOXICITY OF CAFFEN.

engorged and friable; gall cyst well filled; stomach exhibited catarrhal
tion of mesenteries and intestines; kidney showed marked cortical
The results of the experiments of this series likewise indicate that the
hare is more resistant to caffein than the rabbits of other varieties Thus, of the four
gray rabbits (Nos. 235, 316, 395, and 396), which received 267 to 283 mg of per
kilo, two died and two lived,a one of which, 96, showed the presence of coccidiosis
of the liver. On the other hand it will be observed that the black and white rabbits
which received from 270 to 275 mg of caffein per kilo all died from the effects of the
drug; one within 1 hour and 25 minutes and another within 50 hours after the admin-
istration of the caffein, while No. 340 died in the night. Furthermore it will be note
that of the last three rabbits of this series, which were Belgian hares and received
290, 293, and 300 mg of caffein, two died six hours after the injection, while the other,
No. 397, lived three days. The minimum fatal dose of caffein for Belgian hares is,
therefore, about 290 to 300 mg per kilo when injected subcutaneously, which is about
50 per cent greater than for rabbits of other varieties.
SERIES E.
It was shown in series A that 0.15 caffein per kilo caused symptoms of intoxication.
Before concluding, however, that this is the smallest dose which causes symptoms of
poisoning, a number of experiments were performed with smaller doses. It was
found that in the great majority of cases 0.1 caffein per kilo may cause diuresi
but no nervous or muscular symptoms. In some rabbits, however, even such a dose
proved fatal. Post-mortem examinations in these cases showed te presence of
coccidiosis of the liver, and it will be recalled that similar observations were made
before. It is quite possible, therefore, that coccidiosis of the liver is an important
factor in decreasing the resistance to caffein. Experiment 551 (p. 25) show that
other conditions may likewise increase the toxicity of caffein.
Rabbit 325. White, female. Weight, 1,065 grams. Diet, oats.
March 17: 11 a. m., 6 cc 2 per cent (112 mgper kilo) caffein injected subcutaneously
in the back. About 5 cc of urine squeezed out from bladder before injecting caffein.
March 17: 1 p. m., hind legs crossed and stretched out, front legs also extended;
rabbit lying stretched out on her belly.
March 17: 5.40 p. m., rabbit still alive, condition somewhat improved.
March 18: 9 a. m., found dead, stiff and cold. Autopsy: Hemorrhagic area at point
of inoculation; subcutaneous region of both thighs presented a hemorrhagic in
tion of the tissues; liver contained lesions of coccidiosis; other organs appently
normal.
Rabbit 330. Belgian hare, female. Weight, 95 grams; poorly nourisd.
March 18: 3.35 p. m., 5 cc 2 per cent caffein (107 mg per kilo) injected into subcu-
taneous tissues in the back; 5.30 p. m., no symptoms.
March 19: 9 a. m., no symptoms.
March 25: Weight, 825 grams.
Rabbit 329. Belgian hare, male. Weight, 775 grams; poorlyhed Receied
March 18.
March 18: 3.30 p. m., 4 ce 2 per cent caffein (103 mg per kilo) injected into sub-
cutaneous tissues in the back; 5.30 p. m., no symptoms.
March 19: 9 a. m., no symptoms.
March 25: Rabbit alive in good condition; weight, 825 gras.
abbit 320. Black, male. Weight, 1,040 grams. Diet, oats.
March 17: 11 a. m., 6 cc 2 per cent caffein (115 mg per kilo) injected subcutaneously
in the back; only a few drops of urine obtained from bladder before injectin
1 p. m., rabbit very retless; ran away when placed on floor; cried when to ed with
a pice of paper; no tremors observed, but rabbit became exhausted and was unable
to walk; legs extended out; after running for about a miute dypna was very
marked, but rabbit n raised himself on his legs; 5.40 p. m., rabbit p on his leg.
a urvved rst dose.







ACUTE INTOXICATION-RABBITS. 25

S18: 9 a. m., found dead, but still warm. Autops: Lungs studded with
all grayish white nodules, adhesions to costal pleura; probably lesions of coccidiosis;
liver studded with coccidiosis nodule. Hemorrhages at point of inoculation.
b 51. Gray, femae. Weight, January26, 1,650 grams. Diet, oats; fed 20 cc of
25 per nt alcohol daily from January 26-31.
January 31: Weight, 1,450 grams; 10.20 a. m., temperature 101.6; 10.45, a. m.,
temperature 101.60; received 7 cc 2 per cent caffein subcutaneously into back; 11.15
a. ., convusions of short duration; raised himself on posterior legs, anterior legs
wide apart; 4.10 p. m., looked normal, not hypersensitive; 4.30 p. m., condition
seemed to be good.
February 1: 9 a. m., found dead, was alive at 5.30 p. m. of previous day. Autopsy:
Lesions found involved thoracic cavity mainly; lungs were hepatized and a fibro
lastic exudate caused them to adhere to costal pleura; liver engorged and appeared
atty; no marked lesions affecting digestive tract, a slight catarrh of stomach being
the only noticeable feature; kidneys and spleen normal.

TABLE 1.-Subcutaneous injections of cafein-rabbits.

SERIES A.


No. Weight Ap ce of syiTp Duration of life. Diet. Remarks.
t toms in-
kilo.

Grams. Mg.
332 1,070 18 1 hour 45 minutes..... Survived.............. Oats..... Gray.
331 1,170 153 .... do................ ....do................ ...do..... Do.
328 1,200 1 ....do............... .....do............... ..do..... .. .. Do.
322 1,065 160 1hour ...................do............ ...do..... White.
217 1,35 147 ........................ .....do................ ...do..... Do.
219 1,820 153 ....... ... ... ........ ....do..................do..... Maltese.
194 1,490 174 ....................... ....do............... ...do..... Whte.
191 1,91 167 ........................ ....do ................ ...do..... Light brown.

SERIES B, GROUP I.

19 1,478 210 2 hours 0 minutes.... 3 hours 10 minutes.... Oat..... White.
9 1,85 200 1 hour .............. About 1 hours....... ...do..... ray white.
112 875 20 30minutes............ .....do......: ............do..... Black.
119 1,060 188 ............................do................ do ....... Yellow white.
19 1,300 200 .................3 hours 10 minutes.... Carrots.. White.
208 1,068 188 2 hours .............. About 24 hours....... ...do..... Gray.

SERIES B, GROUP II.

247 1.295 200 2.5 hours.............. Survived.............. Oats,.... Gray.
248 1,30 200 3hours................ .....do............... do.... o.
337 1040 211 1. hours.............. ....do.............. Carrots.. Do.
1, 211 ....do................ .....do............... ...do..... Do.

SERIES C.

122 2 060 250 2 hours 5 minutes... 1.5 days............. Oats..... White.
234 1,660 242 ...................... A u24 hours....... Carrots... Do.
335 1,170 240 1hour............... .. do.............o... tdo ..... Gray cocidosis.
249 1,185 36 4 hours.................. urvived........... Oa t..... ry.
321 1,135 246 2 hours 10 mnutes.... .....do................ ...do..... Yelow
250 1.3 252 4 hours ) minuts.. ._...do .......,. .......dot,.... ra
334 1270 240 1hour ............... .....do.............. Carro t... bo.
233 1,075 238 hoursl0minutes.... 21hours............ .....do..... White.







26 THE TOXICITY OF CAFFEIN.

TABLE 1.-Subuaneous inections ofcafein-rabbi-Con

SERIES D.

Caffein s
No. Weight. p Appea e of symp- Duration of life. Dt. Remarks.
kilo. tOs n-

Grams. Mg.
253 1,600 275 10 minutes........... 35 minutes............ Oats..... Brown and black.
252 1,335 270 30 minutes........... 4 hours 55 minutes.... ...do..... Black.
327 820 292 .................... 2 hours 15 minutes......do.....White.
340 1,465 273 .................... About 18 hours........ ...do..... Whteand brown.
341 1,450 270 ............ ......... 1 hour 25 minute....... do ..... Do.
326 1,645 243 2 hours................ 50 hours ............ ....do.....White.
235 1,875 267 ........................ 20 hours........... Carrots... Gray.
316 860 267 2 hours 45 minutes.... 3 hours 20 minutes... Oats.. Do.
395 1,410 283 3 hours............... Survived ............. ......... Do.
395 1,215 275 .....do................ About 2 days......... Oats..... Do.
396 1,475 272 ....do.............. Survived.............. do..... Do.
396 1,245 275 1 hour................ About 18 hours......... do..... Do.
397 1,375 290 ...................... 3 days................ ..do..... Do.
398 1,570 293 ................... 5.5 hours.............. ..do.... Do.
399 1,725 300 .. ...................6 hours............ ... do..... Do.

SERIES E.

325 1,065 112 2 hours .............. Less than 22 hours.... Oats..... White female.
330 935 107 None.................. Survived............. ........ Gray.
329 775 103 ....do............... .....do................ ......... Gray male.
320 1,040 115 2 hours................ 46 hours............... Oats..... Black male.
551 1,450 100 30 minutes.......... Less than 24 hours.. ...do.... Gray female


ADMINITSTRATION BY MOUTH.

These experiments were carried out on two varieties of rabbits, the white and the
gray. The diet consisted chiefly of oats, but in a few cases carrots formed the exclusive
diet. Food and water were given ad libitum. A 2 per cent solution of caffein wa
administered through a stomach tube. Since the resistance to most dru is com-
monly supposed to be greater when given by mouth than when administered by any
other path, doses of 175 to 200 mg per kilo were fed in a series of preliminary experi-
ments, all of which were performed on gray rabbits weighing from 865 to 1,135 grams,
and which were fed carrots for several days previous to the experiment. hree of the
rabbits survived, two without showing any symptoms; in the other case paralysis of
the posterior extremities was observed five hours after he received caffein and he was
found dead the next morning. Unfortunately no autopsy was performed. The low
resistance to caffein of this animal was probably due to some abnormal condition which
developed about the time of the experiment, since this rabbit received 325 mg of
caffein per kilo two weeks previously and increased reflexes only were observed as a
result of this treatment. Hence 200 mg of caffein per kilo can not be considered the
toxic dose when fed by mouth. In the following experiments larger doses were
therefore given.
SEJRIs A.

Rabbit 248. Belgian hare. Weight, 1,170 gams. Diet, oats.
November 17: 1.20 p. m., 19.5 cc 2 per cent caffein (330 mg per kilo) administered
by the mouth; 4.30 p. m., somewhat hypersensitive.
November 19: No symptoms; at 9 a. nm., urine collected, no reduction of Fehling's
solution; rabbit survived.
Rabbit 241. White mae. eiht, 1,380 rams. Diet, oats.
November 17: 1.15 p. m., 20 cc 2 per cent caffein (290 g per kilo) administered
by the mouth; 4.30 p. m., some hyperensitiveness, but no other symptoms.
November 18: 9 a. ., rie collected, no reduction of F ling solution; no
symptoms; rabbit survived.







ACUTE INTOXICATION-RABBITS. 27

Rabbit 49. Belgian hare. Weight, 890 grams. Diet, oats.
November 17: 1.30 p. m., 14.5 cc 2 per cent caffein (325 mg per kilo) administered;
4.30 p. m., hypersensitiveness; no other symptoms.
November 18: 10 a. m., no symptoms; urine collected, no reduction; rabbit sur-
vived.
SERIES B.

The object of these experiments was to determine the minimum fatal dose of caffein
in the two varieties of rabbits, the white and the gray. All of the animals selected
were approximately of the same weight.
Rabbit 289. Belgian hare, male. Weight, 935 grams. Diet, oats.
November 19: 4 p. m., 17 cc 2 per cent caffein (363 mg per kilo) administered by
mouth, followed by 10 cc of 0.9 per cent salt solution.
November 20: Urine examined, no sugar found, no symptom noticed at any time
after injection.
Rabbit 254. Belgian hare, female. Weight, 975 grams. Diet, oats.
November 19: 4.05 p. m., 18 cc 2 per cent caffein (369 mg per kilo) administered by
mouth, followed by 10 cc of 0.9 per cent salt solution.
November 20: 9 a. m., rabbit found dead.
Rabbit s67. White. Weight, 1,050 grams. Diet, oats.
November 23: 12.10 p. m., 18 cc 2 per cent caffein (342 mg per kilo) given by mouth,
followed by 18 cc salt solution; 1 p. m., increased reflexes, tremors marked but no teta-
nus; 1.05 p. m., rabbit stretched on abdomen, posterior extremities in ext ended position
and paralyzed, soon after clonic spass set in, which recurred about every minute;
1.14 p. m., tetanus and death. Autopsy: Liver showed fatty degeneration; slight in-
flammation of stomach and intestines; other organs normal.
Rabbit 268. White. Weight 1,100 grams. Diet, oats.
November 23: 20 cc 2 per cent caffein (363 mg per kilo) administered by mouth, fol-
lowed by 20 cc salt solution; 1.15 p. m., somewhat hypersensitive; 4.30 p. m., tremors
fairy marked, no urine passed, about 2 cc of bloody looking urine obtained from blad-
der, which contained albumen and a considerable amount of glycogen; rabbit died.
Rabbit 419, Belgian hare, male. Weight, 1,600 grams. Dit, oats.
September 26: 10 a. m., 28 cc 2 per cent caffein (350 mg per kilo) given by mouth;
reflexes increased at 4 p. nm.; 6 p. m., reflexes still increased, no other symptoms.
September 27: 9 a. m., found dead. Autopsy: Lungs, liver, and kidneys congested;
other organs normal.
Rabbit 420. Belgian hare, male. Weight, 1,250 grams. Diet, oats.
September 26: 10 a. im., 22 cc 2 per cent caffein (352 ig per kilo) given by mouth;
11.35 a. m., convulsions; 12 noon, found dead. Autopsy: Liver showed very extensive
coccidioss; no other lesions.
Rabbit 421. Belgian hare, mal. Weight, 1,485 grams. Diet, oats.
September 26: 10 a. m., 26 cc 2 per cent caffein (351 mg per kilo) administered by
mouth; 4 p. ., reflexes increased; 6 p. m., reflexes as before, no tetanus observed.
September 27: 9 a. m., rabbit found dead. Autopsy: Congestion of lungs and kid-
neys; liver congeclst and slightly fatty.
Rabbit 44. White, rale. Weight, 1,295 grams. Diut, oats.
September 26: 2 p. im., 19 cc 2 per cent tcaffei (293 ng per kilo) administered by
mouth; 4 p. i., relexes incrased, no other synptoms; 6 p. m., no change since 4 p. n.
September 27: 12 noon, convulsions and deat Autopsy: Congest in of the lIung;
no other lesions.
Rabbit 43. hite, e Weiht, 1, 05 grail. Diet, oats.
September 26: 2 p. m., 18 cc 2 per cent caffein administered by mouth; 4 p. m.,
rexes increasel, dno tetamn; 6 p. m., condition unchanged since 4 p. m.
September 27: 9 a. inm., found dead. Autops: Lungs liver, and kidrneys congested;
other organs normal.
Rabbit 422. White, male. Wight, 1, grams. Dit, oats.
September 26: 2 p. m., 21 cc 2 per cent caffein (291 mg per kilo) given by mouth;
refexe increased at 4 p. m.
September 27: 3 p. m., alive, no sympto ; 4 p. convulsions with recvery, this
s s followed by a iolent attack of ttanus, which lste about one minute and
was succeeded by pralysis, rbbit died at 4.30. Autpay.: Liver slightly congste:d;
a small rtionp of the inetine sowed conetion ad edoma; other orans normal.







28 THE TOXICITY OF CAFFEIN.

A study of these experiments shows also considerable variation toxicity of
caffein when given by mouth. In some cases a dose of 300 mg per kilo, and even le
caused death, as in rabbits 423 and 424. In other rabbits, however, appro tely the
same doses of caffein produced increased reflexes only. The same symptoms were pro-
duced in Nos. 248 and 249 after the administration of 325-330 mg of caffein per kilo,
while another rabbit (No. 239) survived a dose of 363 mg per kilo. That this is excep-
tional, however, appears from the result of the following experiments on rabbits
Nos. 419, 420, and 421, all of which died after receiving 350 mg of caffein per kilo, and
rabbits 267 and 268, to which doses of 363 and 342 mg, respectively, per kilo proved
fatal. It will be observed further that the gray rabbits are more resistant to caffein
than the white animals, as 350 mg per kilo was the smallest fatal dose for rabbits 419;
420, and 421, all of which were gray rabbits, while a dose of 290 mg per kilo was fat
for some of the white rabbits. Again, it will be noticed that of the two gray rabbits,
Nos. 254 and 239, which received the largest doses in these experiments, namely, 369
and 363 mg, respectively, one survived. The largest doses given to the white rabbits
were 363 and 342 mg caffein per kilo. Both of these died from the effects of the drug.
It may be concluded, therefore, that the minimum toxic dose for the gray rabbit is
about 325 mg of caffein per kilo, and the minimum fatal dose is at least 350 per kilo.
It is to be remarked in this connection that post-mortem examination showed ex-
tensive coccidiosis in rabbit 420 and fatty liver in No. 421, while the macrocopical
examination of the organs of Nos. 424 and 423 failed to show the presence of such
abnormalities. Since, as was observed in the section on subcutaneous injection and
elsewhere in this investigation, pathological changes are apt to decrease the resistance
to caffein, it is quite possible that 350 mg per kilo is not the minimum fatal dose for
the normal rabbit. Indeed, the experiment on rabbit 239 lends support to this
view, thus furnishing additional evidence of difference in the ce to caffein
in the two varieties of rabbits.

TABLE 2.-Administration of caffein by mouth.
SERIES A.

Rab- Caffei
bit Weight. Symptoms. Duration of life. Diet. Remarks.
No. per kilo.

Grams. Mg.
248 1,170 330 3 hours 10 minutes..... Survived................. Oat....ra
241 1,380 290 2 hours 15 minutes.........do.............. ..do... White male.
249 890 325 3 hours................. .....do................. do.... Gray male.

SERIES B.

239 935 363 ......................... Survived........ ..... Oats.... Gray male
254 975 309 ....................... About 2 days..............do.... G female.
267 1,050 342 5 mintutes............. I hour 4 minutes........ ...do.... Whte.
268 1,100 363 ........ ............. About 3 hour.............do.... Do.
419 1,Io0 350 6 hours ................ Less than 24 hours...... .. do.... Graymale.
420 1,250 352 hour minutes..... ouuts......rs ................. ...do.... Do.
421 1,485 351 ours................ Le than hours...... ...do.... Do.
424 1.295 293 2hours .......2 lio.... hour................. ..do.... it ale.
423 1,206 300 ..... do................. Less than 19 hours...... ...do.... Do.
422 1,440 291 ....do................ hours...................do.... Do.

INJECTION INTO THE PERITONEAL CAVITY.

In a number of experiments caffein was introdced into the peritnal cavity.
Rabbits of different varieties receiving a diet of oat or carro were employed for this
rpose; f and water were given ad libitum. The minimum doses required to
induce symptoms or cause death in these animals were determined; test with caffein
were also mae on young rabbits in order to study the influence of age on theretnce
to this ubstance. The rHults are show in the followin experimfnts:






ACUTE INTOXICATION-RABBITS. 29

SERIEs A.

In series large doses were administered, approximating 0.3 gram per kilo.
Rabbit71. Gray female. Weight, 1,659 grams.
Ja y 20: 2.20 p. m., 25 cc aqueous solution 2 per cent caffein (300 mg per kilo)
were injected into the peritoneal cavity; 3.45 p. m., when doors of cage were opened
rabbit ad spasm of ort duration.
y 21: Rabbit found dead.
S7. Gray and white. Weight, 1,402 ams
Jan y 21: 11.17 a. m., 20.2 cc (aqueous solution) of 2 per cent caffein (300 mg
per kilo) ijected into peritoneal cavity from burette; 11.25 a. m., paralysis; 11.30
a. m., rabbit had convulsion when picked up from the floor, followed by several
later; 11.35 a. m., typical tetanus; 12.30 noon, found dead.
Rabbit 61. Black female. eight, ,1 grams.
January 19: 40 cc 2 per cent caffein, aqueous solution (300 mg per kilo), injected
into peritoneal cavity from burette; tetanus when about 30 cc were injected; when
removed from holder, repeated and violent convulsions, terminating in death.

SERIES B.

The object of these experiments was to determine the minimum lethal dose; 0.2 to
0.15 gram of caffein per kilo was injected into the rabbits of this series.
Rabbit 69. Whie female. Weight, 1,714 grams.
January 20: 10.15 a. m., 6 cc 2 per cent caffein, aqueous solution, injected into
peritoneal cavity. No symptoms, under observation for 45 minutes, rabbit defecated
rather copiously; feces were soft; 11 a. m., 6 cc 2 per cent caffein, aqueous solution,
injected into peritoneal cavity, no symptoms, under observation for 40 minutes; 11.40,
8 cc 2 percent caffein injected into peritoneal cavity; 11.45, rabbit is restless, reflexes
increased.
Rabbit 70. Gray and white female. Weight, 1,487 grams.
January 20: 1.30 p. m., 15 cc 2 per cent aqueous solution of caffein (0.2 gram per
kilo) injected into the peritoneal cavity; 2.20 p. m., no symptoms.
January 30: About 2 p. n. rabbit died.
February 1: Autopsy: Cirrhosis of the liver; enteritis of small intestines; stomach
and kidneys normal.
Rabbit 93. Maltese, male. Weight, 1,197 grams.
March 2: 11.30 a. m., 12 cc of 2 per cent caffein (200 mg per kilo) injected into
peritoneal cavity; 11.35 a. m., while being released from holder, tetanus occurred,
repeated attacks later, clonic convulsions with tonic rigidity of posterior extremities
duringtheattacks as well as during intervals, anterior extremities were relaxed during
the intervals between the attacks, opisthotnos of cervical region but kyphosis in
lumbar region were observed, no salivation nor dilatation of the pupils; 2 p. m.,
rabbit died.
Rabbit 92. Yellow female. Weight, 1,388 grams.
February 25, 4.15 p. m., 14 cc 2 per cent caffein (0.2 gra per kilo injected into
peritoneal cavity; 4.20 p. m., restlessness and increased reflexe, rabbit found stretche
out in cage, but raise himself on hi les again; 4.4, general tremor when touched.
February 26: 9 a. m., rabbit found dead. Autopy: Hemorrhage into abdominal
muscles at site of injection; hemorrhage also in walls of stomach opposite similar
spot in abdominal wall.
Rabbit 309. Belgian harefeinale. Weight, 1,500 grams. Did, oats.
March 2: 2.05 p. m., 2 per cent caffein luion (0.2 gn per kilo) injeed into
peritoneal cavity; 2.25 p. m., found dead, no urine found in blader.
Rabbit 307. Belgian hare,female. WRight, 1,!320 gams. Dit, oats.
March 2: 12 noon, urine obined fro bladder, clear amber colord, no albumin,
no reduction; 12.06 p. m., 10 cc of 2 per cent caffin (0.151 gram per kilo) injected
into peritoal cavity; 1.30 p. m., rabbit placed on fl(r, runs aroun but anterior and
posterior extremiie soon extended, in tonic condition; 2.25 p. m., reflexes incred,
paralyi of extremitie, dyspncea; 4.5 p. m., about 100 cc urine collted, no
albumin, reduction of Fehlin's solution moderate.
March 3: 9.30 a. in., posterior extreities extended and rigid, anterior extremitie
paralyzed, respiration less frequent and deeper than normal. iabbit died at 11.50
a. .; m e collected since 4.50 previous day gave very heavy reduction of
Flin's solution. Auto : Amal in condition; in the left axillary reion







30 THE TOXICITY OF CAFFEIN.

was observed a hemorrhage into the subcutaneous and musmilar tissue of that region.
The ventral portion of the large colon, in contact with the ventral abdominal wall,
showed a hemorrhagic area about one-half inch in length, such as might be roduced
by a puncture or bruise of the colon through the abdominal wall. A small portion
of the small intestine adjacent to the colon was affected in a similar manner All
internal organs were apparently normal.
Rabbit 308. Belgian hare, female. Weight, 1,350 grams. Diet, oats.
March 2: 11.45 a. m., urine obtained from bladder, no albumen, o reduction;
11.50 a. m., 10 cc 2 per cent caffein (0.15 gram per kilo) injected into peritoneal cav-
ity; 1.30 p. m., not very active, no abnormal symptoms otherwise; 3. 30 p. ., rabbit
looked depressed, made very little attempt to move about, remained in e position
most of the time when placed on floor; 4.30 p. m., 180 cc urine collected, no albumen
reduction of Fehling's solution moderate.
March 3: 9.30 a. m., rabbit looks normal, is able to walk but is easily fatigued when
made to walk about or when placed on his side, followed by paralysis of anterior
extremities, posterior extremities apparently normal, about 90 cc of urine collected
at noon was free from albumen, did not reduce Fehling's solution.
March 4: 11 a. m., lying on his side in cage, anterior extremities limp, pterior
extremities extended and rigid, is in dying condition.
March 5: 9 a. m., found dead. Autopsy: Liver engorged; spleen congested, but
not enlarged; kidneys, some congestion in cortex; stomach filled, mucoa thickened
and easily pulled off; petechial hemorrhages on serosa of colon.

SERIES C.

The experiments of this series were made to determine the minimum toxic dose.
Rabbit 295. Belgian hare, female. Weight, 1,205 grams. Diet, carrot.
March 1: 10.40 a. m., 6 cc 2 per cent caffein (0.1 gram per kilo) injected into pei-
toneal cavity; about 2 cc of urine obtained before injecting caffein; 2 p. m, 100 cc
urine, bloody in appearance, collected, a moderate quantity of albumen present, no
reduction; 3.40 p. m., no symptoms.
March 4: 2 p. m., rabbit looks well.
Rabbit 293. Belgian hare, female. Weight, 1,605 grams. Diet, carrots.
March 1: Urine from bladder clear, alkaline; 11.55 a. m., 8 cc 2 per cent caffein
(0.1 gram per kilo) injected into peritoneal cavity; 3 p. m., 90 cc urine normal in color
collected, no albumen, no reduction; 3.40 p. m., no symptoms.
March 4: 1.15 p. m., rabbit looks normal.
Rabbit 92. Belgian hare, male. Weight, 1,595 grams Diet, carrots.
March 1: 10.10 a. m., 8 cc 2 per cent caffein (0.1 gram per kilo) solution injected
into peritoneal cavity; 10.40 a. m., rabbit urinated, reflexe increased, but no other
symptoms; 10.50 a. m., no urine obtained from bladder; 2 p. m., 105 cc of clear pale
urine collected; no albumen, no reduction; 3.40 p. m., no symptoms.
March 4: 2 p. m., rabbit looks well, urine collected, did not contain sugar.
Rabbit 298. Belgian hare, female. eight, 1,05 grams. Diet, carrots.
March 1: 4.06 p. nr., 7.5 cc 2 per cent caffein solution (0.125 gram per kilo) injected
into peritoneal cavity, urine obtained from bladder immediately fter injection, no
albumen, no reduction; 5.30 p. m., reflexes increased, rabbit was able to run around,
but became paralyzed soon; 5.40 p. m., rabbit is ain able to run around.
March 3: 10 a. m., anterior extremities paralyzed, is able to use posterior extremi-
ties.
March 4: 1 p. m., rabbit looks normal.
Rabbit t23. Belgian hare, male. Weight, 1,165 grams. Diet, carrots.
March 1: 3.50 p. m., urine obtained from bladder clear, amb colored, no albumen,
no sugar; 3.52 p. m., 7.5 cc 2 per cent caffein (125 mg per kilo) injected into pi-
toneal cavity; 5.40 p. m., rabbit makes little attempt to run when put on the oor,
weNkness of extremities marked.
March 4: 1.15 p. m., rabbit normal.
SERIS 1)D.

The object of the experiments of this series was to study the effect of age on the
resistance to caffein, Half-grown rabbits were, theefore, sed in the followin experi-
ments.
Rabbit 310. Belgan hare, fmale. eight, 880 grams. Dit, oats.
March 2: 3.25 p. m., 9 cc 2 per cent caffein (0.2 gram per kilo) injected into peri-
toneal cavity.






ACUTE INTOXICATION-RABBITS. 31

March 3: 9.30 a. m., no symptoms, rabbit looks normal.
M h 4: 11 a. m., posterior extremities abducted, walked when placed on the
floor, made no attempt to change attitude when placed on its side, remained some
time in this position.
March 5: 9 a. m., found dead. Autopsy: Liver showed areas of degeneration;
dney congestion and pete al hemorrhge on cortex; small and large intestines,
tion marked; bladder distended.
Rabbit75. Gray and white, female. Weight, 842 grams.
January 25: 3 p. m., 8.5 cc 2 per cent caffein solution (0.2 gram per kilo) injected
nto peritoneal cavity; 3.15 p. m., anterior extremities weak and reflexes increaed.
January 27: Rabbit paralyzed but is able to turn over when placed on back.
Rabbit 74. Gray and white, female. Weight, 692 grams.
January 25: 3 p. m., 7 cc 2 per cent caffein (0.2 gram per kilo) solution injected
intoperitoneal cavity; 3.15 p. m., reflexes increased and anterior extremities paralyzed.
January 27: Rabbit recovered and is able to walk about in the room.
Rabbit 12, maltese, female. Weight, 740 grams. Diet, oats.
March 3: 11.47 a. m., urine obtained from bladder, appearance normal, no albumen,
o reduction of Fehling's solution; 11.50 a. m., 7.5 cc 2 per cent caffein (0.2 gram per
kilo) injected into peritoneal cavity; 2.30 p. m. anterior extremities paralyzed, pos-
terior extremities rigid d extended; 5 p. m. (about), rabbit died.
Rabbit 311. Belgian hare,female. Weight, 650 grams. Diet, oats.
March 3: 11.26 a. m., urine obtained from bladder normal in appearance, albumen
considerable, reduction of Fehling's solution none; 11.27 a. m., 6 cc 2 per cent caffein
olutin (0.2 gram per kilo) injected into peritoneal cavity; 2.30 p. m., rabbit seemed
to be normal, no ymptoms had developed; urine collected contained a lare amount
of sur, reduction was very heavy, but no albumen was found.
March 4: 11 a. m., condition good, moves about when put on floor; gait, normal.
Rabbit 78. Yello and white. Weight 659 grams.
Jauary 26: 1.30 p. m., 8.5 cc 2 per cent caffein (250 mg per kilo) injected into
peritoneal cavity, under observation the rest of the afternoon, no symptoms.
January 27: 4 p. m., no symptoms developed.
Rabbit 317. Belgian hare, female. Weight 635 rams. Diet oats.
March 15: 10.35 a. m., 8 cc 2 per cent caffein (0. 252 gram per kilo) injeted into
peritoneal cavity; 12 noon, marked abduction of hind legs, wa unable to walk after
a little exertion, rabbit died between 12.30 and 12.50 p. m. Autopsy. ight lung
hepatized an showed adhesions to costal and mediastinal pleura; liver studded
with nodules of coccidiosis; splen congeste stomach filled, mucs normal intes-
tines injected colon hemorrhagic on serosa in ventral region, near point of injetion;
kidneys normal.
Rabbit 3. White,female. Weight 820 grams. Diet oats.
March 15: 10.45 a. m., 10 cc 2 per cent caffein (20 mg per kilo) injected into pe-
toneal cavity; 12 noon, reflexes increased, hind legs abducted but is able to walk,
s ptom are mild; 1.40 p. m., tremors, weakn and abduction of head and legs
much more marked tan at 12 noon.
March 16: Condition good.
March 17: Cndition good, recovery apparently complete.
Since the experiment of Series A, which were intended as preliminay tes, have
shown that 0.3 gra of affein per kilo hen intruced into the pritoneal cavity i
rapidly absorbed and is fatal, uch smaller dses were employed in subsequent
trials wit the drg. This is shown in series B, which may be divided into two
groups. Grop consisting of rabbits 69, 70, 92, 93, ad 309, which recived 0.2
Sof caffein per kilo, and Group II, Nos. 307 and 308, into which 0.15 mginn of
caffein per kilo was injected. Three rabbits of Group I (No. 92, 93, 309) died from
theeffectsof caffei; rbbit 309 twenty iutes afterinjection, and rabbits Nos. 92
and 93, twenty hours and two and one-half hors, r vely, ater the admtion
of caffein. In both of these rabbit symptos appeared within five inu after the
njections were made. Rabbit 69 and 70, it will be noticed, survived the une
amount of caffein in proportion to body weight was given to the other membrs of
thisgroup. Increased and the distribtion of the dose may account for the
greater resistance of rabbit No. 69. The cae of rabbit No. 70 is vidently one of ex-
resistance to i, since both the bbits of Grou II died from the effects






32 THE TOXICITY OF C F N.

of a much smaller dose, ely, 0.15 gram of caffein per kilo. Mor
examination at the autopsy of Nos. 307 and 308 failed to show any h
tend to lessen the resistance to caffein.
That a dose of 0.15 gram per kilo is therefore in all probability the minimum fatal
dose for the rabbit when injected into the peritoneal cavity apfrom the results
of the experiments in series C, in which smaller doses, 0.125 of caffein kilo
caused mild symptoms only, while 0.1 gram per kilo rarely induced any symp
It may be remarked that the rabbits of series C were fed carrotshile rabbits Nos 307
and 308 received oats. Their resistance to caffein may be different, but, as was
pointed out in the earlier part of this investigation, diet does not seem to influence the
toxicity of the single dose of caffein. Doses of 150 and of 100 to 125 mg per kilo, wh
injected into the peritoneal cavity, may be considered, respectively, as the minimum
fatal and minimum toxic doses for the gray rabbit. Analysis of the experiments in
series D shows much greater resistance to caffein than in the other rabbis which
received it intraperitoneally. Thus, after the administration of 0.2 gram per kilo to
each of five rabbits, no effect was observed in two cases (Nos. 310, 311), while in two
others (Nos. 74, 75) symptoms developed, but they survived. Only one rabbit, No.
312, died from the effects of this dose; the autopsy showed the presence of degenera-
tion of the liver and petechial hemorrhages on the cortex of the kidneys in the case of
No. 310, which was probably the cause of death rather than the caffein.
Two decigrams of caffein can not be considered, therefore, the fatal dose for rabbits.
This is further corroborated by the results obtained in experiments with larger doses.
Rabbit 78, which received 257 mg per kilo, failed to show any symptoms. The same
amount in proportion to body weight in No. 323 caused mild symptom only, while
the rapid death of rabbit No. 317 after the same dose of caffein may be explained by the
lesion found at autopsy, thus affording additional evidence that disease may
the resistance to caffein. It will be observed that all the members of this series were
young rabbits and, as will be shown later, young animals of other species are lik
more resistant to caffein than adult animals. Similar results were obtained by von
Anrep, who observed that atropin is less toxic in young than in full-grown animals
Observations were also made on the diuretic effect of caffein when injected into the
peritoneal cavity. The results shown in the following table indicates the stimulating
effect on renal secretion whether the diet consisted of oats or of carrots. The urine of
some rabbits contained moderate amounts of sugar after from 0.2 to 0.15 gram of caffein
per kilo was given; albumen was observed in one case, but in none of the others. In
rabbit No. 311 albumin was found before the injection of caffein, but none in the urine
which was collected three hours after caffein was injected.

Effect of cafein on renal secreto.


No. Weight. af Urine. e Det.

Grams. Gram. cc.
307......... ....... ........ ............ 1.320 0.150 100 4.5 hours...... Oats.
3M ........................................ 1,305 .150 180 .....do........ Do.
2 ....................... .......... ..... 1, .100 100 2ho rs2 i Carrots.
utes.
293 ... ..... ......................... ... 1 .100 0 ... .. Do.
2 ........................................ 1,5 5 .1 10 4 ho ..... .

No.Th amount f urine red n three hours by ntrol rabbits, on a carrot diet, varied between
35 and 50 cc, the averag weight of the animals bein a Itte above 1,00 gra. The s n of
on an oat diet was much less for an equal period of time.







ACUTE INTOXICATION-RABBITS. 33

TABLE 3.-Intraperitoneal injections.

SERIES A.


No. Weight. Caffein Time of appearance of Duration of life. Remarks.
per kilo. symptoms.

Grams. Gram.
71 1,659 0.3 85 minutes............ 24 hours......... Gray.
61 2,143 .3 .................... At the end of injection.. Black.
72 1,402 .3 8 minutes............. 1.25 hour ............... Gray and white.

SERIES B, GROUP I.

70 1,487 0.2 ........................10 days............... Gray and white.
93 1,492 .2 5 minutes............. 2.5 hours............... Maltese; given second
dose after 3 days, died
2.5 hours later.
69 1,492 .2 About 5 minutes...... Survived .............. White.
92 1,388 .2 5 minutes............. 24 hours.............. Yellow.
09 1,00 .2 .................... 20 minutes............. Belgian; oats.

SERIES B, GROUP II.

308 1,350 0.15 3 hours and 40 minutes. About 2.5 days.......... elgian; oats.
3107 1,320 .15 1 hour 24 minutes...... 24hours................ Do.

SERIES C.

223 1,165 0.125 2 hours............. Survived............... Belgian; carrots.
293 1,605 .1 ... ...... ....... ......... do ................. Do.
295 1,205 .1 ................... .....do. ................ Do.
292 1,595 .1 ........................ .....do........ .......... Do.
298 1,205 .125 1.5 hours.......... .... do.................. Do.

SERIES D.

310 880 0.2 2 days 1................ About 2.5 days I........ Belgian; oats.
1 650 .2 .................. Survived............. Do.
312 740 .2 40 minutes............ 4.5 hours................ Maltese; oats.
78 659 .257 15 minutes............ Survived............. Yellow and white; oats.
75 842 .2 .....do .. .. .............do................ Gray and white.
74 692 .2 .....do.....................do.................
17 635 .252 1 hour 25 minutes ..... About 2 hours......... Belgian; oats.
33 820 .25 1 hour 15 minutes ..... Survived ........ ..... White; oats.

1 Not due to caffein.

INTRAMUSCUL ARB INJECTION.

Well-fed rabbits, which received a diet exclusively of oalt, were used for these
experiments. The injections were made into the lumbar or into the gluteal mucles.

SERIES A.

In his series the caffein was injected into the gluteal muscles.
Rabbit 84. Broon and white, feml. t, 1,100 grams.
December 14: 2 p. m., 11 cc 2 per cent caffein injected into the gluteal muscles
(0.2 gra per kilo), under observation until 5 p. m., had frequent convulsions; at
5 p. m. in a comatose condition. bbit was found dead the next morning.
Rabbit 86, while and blak, male. ight, 1,15 grams.
December 15: 2.30 p. m., 13 cc 2 per cent caffein injcted into the gluti l muscle
(0.1977 gram per kilo, tremors and increased r exes o erved during the next two
hours, but no other symptoms.
December 17: abbit alive.
18594-Bull. 148-12---8






34 THE TOXICITY OF CAFFEIN.

Rabbit 285, yellow and white, female. Weight, 1,385 grams.
December 14: 10.15 a. m., 14 cc 2 per cent caffein injected into the gluteal muscles
(0.2 gram per kilo), general tremors, but no convulsions observed. Rabbit survived.
December 17: Rabbit still alive.
Rabbit 87. Belgian harefemale Weight, 1,140 grams.
December 15: 2.15 p. m., 11cc of 2 percent caffein injected int the luteal muscles;
2.30 p. m., tonic contractions of posterior limbs. Paralysis and death at 2.4 p. m.
SERIEs B.

In series B the caffein was injected into the lumbar muscles.
Rabbit 307. Belgian hare, female. Weight, 1,175 grams.
February 16: 11.05 a. m., 8 cc 2 per cent caffein injected (0.136 gram per kilo) into
the lumbar muscles; under observation until 4 p. m., no symptoms; 4 p. m., allowed
to walk on the floor; after walking a short distance loss of coordination and paralysis
of posterior extremities; 5.20 p. m., found dead.
Rabbit 306. Belgian hare, female. Weight, 1,860 grams.
February 16: 11 a. m., 12.5 cc 2 per cent caffein injected into the lumbar muscles;
12 noon, no symptoms; 2 p. m., walked about 10 feet, exhaustion and paralysis;
3 p. I. found dead.
Rabbit 181. Belgian hare. Weight, 1,230 grams. (Was experimented on some
time previously.)
February 16: 10.55 a. m., 8 cc 2 per cent caffein injected into the lumbar muscles;
(0.130 gram per kilo); 12 noon, no symptoms; 2 p. m., no symptoms; 3 p. m., put on
the floor, walked about 10 feet and was exhausted, posterior extremities paralyzed;
4 p. m., found dead.
SERIES C.

In the fall of the same year additional experiments were carried out with doses
ranging from 100 to 200 milligrams of caffein per kilo, which were injected into the
lumbar muscles. The results are given in the following abbreviated protocols:
Rabbit 425. Belgian hare. Weight 1,520 grams.
September 27: 10.30 a. m., 7.5 cc 2 per cent caffein injected into the lumbar mus-
cles; 2 p. m., reflexes increased.
September 28: Rabbit normal.
October 5: Weight, 1,620 grams; 2.50 p. m., 10 cc 2 per cent caffein injected into
lumbar muscles; 3.05 p. m., reflexes increased.
October 13: Weight, 1,520 grams; 10.30 a. m., 10 cc 2 per cent caffein (131 mg per
kilo) injected; 11 a. m., no symptoms; 11.30 a. m., reflexes much increased.
October 14: Alive, no symptoms.
Rabbit 426. Belgian hare, female. Weight, 1,425 grams.
September 27: 7 cc 2 per cent caffein injected into the lumbar muscles at 10.30 a. m.;
2 p. m., reflexes increased.
September 28: Rabbit normal.
October 5: Weight, 1,425 grams; 2.55 p. m., 9 cc 2 per cent caffein injected into lum-
bar muscles; 3.05 p. m., reflexes increased.
October 13: Weight, 1,405 grams; 10.30 a. m., 10 cc 2 per cent caffein (142 mg per
kilo) injected; 11 a. m., no symptoms; 11.30 a. m., reflexes increased
October 14: Rabbit alive, no symptoms.
Rabbit 427. Belgian hare, female. Weight, 1,780 grams.
September 27: 9 cc 2 per cent caffein injected into the lumbar muscles; 2 p. m.,
reflexes increased.
September 28: Rabbit normal.
October 5: Weight, 1, 850 grams; 3 p. m., 11.5 cc 2 per cent caffn injected into
lumbar muscles; 3.10 p. m., reflexes increased.
October 13: Weigt, 1,830 grams; 10.40 a. m., 14 cc 2 per cent caffein (153 mg per
kilo) injected ino lumbar muscles; 11 a. m., no symptoms; 11.30 a. ., reexes
increased.
October 14: Rabbit alive, no symptoms.
Rabbit 453. Be1lgnio hare, male. Weight, 1,160 grams.
October 12: 3.45 p. m., 11.5 c 2 per cent caffein in aqueous solution injected into
lunmbar musales; 4.15 p. m., reflexes increased; 4.30 p. m., paralyd.






ACUTE INTOXICATION-RABBITS. 35

October 13: 9 a. m., found dead. Autopsy: Gastric mucosa hemorrhagic; liver
dakened; other organs normal.
Rabbit 455. Belgian hare, gray, female. Weight, 1,185 grams.
October 12: 3.30 p. m., 11.5 cc 2 per cent cffein injected into the lumbar muscles;
4 p. m. exes increased.
October 13: Rabbit weighed 1,070 grams, no symptom of caffein poisoning, reflexes
no l; 10.30 a. in., 10 cc 2 per cent caffein injected into the lumbar muscles; 11.30
a. m., jumped off the table, had attack of convulsions and died. Autopsy: Findings
same as in No. 453.
Rabbit 428. Belgian hare, gray, male. Weight, 1,650 grams.
October 5: 4 p. m., 14.8 cc 2 per cent caffein (0.18 gram per kilo) injected into the
lumbar muscles.
October 6: Found dead.
Rabbit 429. Belgian hare, male. Weight, 1,340 grams.
October 5: 4 p. m., 13.5 cc 2 per cent caffein (0.2 gram per kilo) injected into lum-
bar muscles.
October 8: Rabbit found dead.
SERIES D.
Further experiments making injections into both the lumbar and the gluteal muscles,
were made in this series.
Rabbit 577. Gray male. Weight, 1,380 grams.
February 14: 3 p. m. 14 cc 2 per cent caffein injected into the gluteal muscles of
the right side; 3.10 p. m., restless, jumped off the table and walked about, reflexes
increased; 3.45 p. m., passed 30 cc clear, straw-colored urine; 4.45 p. m., allowed to
walk about, ran across the room, about 20 feet, looked tired, stretched himself out on
the floor, then raised himself and walked about showing no disturbance of gait.
February 15: 9 a. m., found dead.
Rabbit 578. y, female. Weight, 1,670 grams.
February 14: 3.05 p. m., 18 cc 2 per cent caffein solution injected into the gluteal
muscles of the right side; 3.15 reflexes increased, but not restless; 5 p. m., allowed to
walk about, no symptoms observed.
February 15: Found dead.
Rabbit 579. White and gray, male. Weight, 1,490 grams.
ebruary 14: 3.15 p. n., 15 cc 2 per cent caffein solution injected into the gluteal
muscles of the right side, put in cage; 3.30 p. m., reflexes increased; 5 p. m., taken
out of cage and allowed to walk across the room, no special symptoms noticed.
February 23: Still alive.
Rabbit 580. Gray male. Weight, 1,510 grams.
February 14: 3.35 p. m., 15 cc 2 per cent caffein solution injected into lumbar
muscles.
February 23: Still alive, in good condition.
Rabbit 81. Gray le. Weight, 1,680 grams.
February 14: 3.45 m., 17 cc 2 per cent caffein solution injected into the lumbar
muscles of the right side; 4 m., reflexes increae; 4.15 p. m., jumped off the table
and had wild convulsions, became very restless, walked about the labortory; 4.25
p. m., had convulsions occasionally; 4.30 p. m., extremities extended and quite rigid;
4.35 p. m., conulsions and death
Rabbit 582. Gray male. Weight, 1,870 grams.
Februar 14: 4.15 p. m., 18 cc 2 per cent affein solution injected into he lumbar
muscles right side; p. ., reflexes increased; walked about in the room, then
rested; 5.15 p. ., had short s when handled
February 23: Alive; g condition.
The data pre ted in thse experients show that the xicity of caffein when
injected into the muscles of the lumbar reons is the same as when inject into the
gluteal mules. Te rabbit of series A received approxiately 0.2 gra affein per
kilo and two died a a relt of this treatment. The other two survived but sympto
of caffein intoxication were observed.
In series smaller doses proved fatal, fro which it would apar that ffein is
more toxic when ije d into the lum mu Further observations, however,
ailed to corroborate the results obtained in this series Thus, in series C, 130 to 150






36 THE TOXITY OF AEIN.

mg of caffein per kilo injected into the lumbar muscles produced mild only
Experiments with larger doses showed that 0.180 gram caffein per
death. It will be noticed, on the other hand, that rabbt No. 45 ved a dose of
0.2 gram per kilo. New experiments were therefore carried out in whh the me
amounts of caffein in proportion to the weight of the animals were injected into the
lumbar muscles as into the gluteal muscles. As shown in the experimentsof D,
one rabbit (No. 581) died shortly after caffein was injected into the lubar mu es;
two recovered. Two of the three which received injections into the gluteal muscles
were found dead the next day; one recovered. Post-mortem examination failed to
indicate the presence of any abnormalities. The rate of absorption of caffein from
the gluteal and from the lumbar muscles seems to be, therefor, the me, or not to
differ very much. The observations of Auer and Meltzer' are of interest in this con-
nection. According to their investigations adrenalin is more rapidly absorbed from
the lumbar than from the gluteal muscles. This is in all probability due to the greater
delicacy of the test they employed (since they judged the rate of absorption by the
effect of adrenalin on blood pressure) as well as to the much greater activity of the
substance.
TABLE 4.-Intramuscular injections.
SERIES A.

afenite of n-
No. Weight Symptoms Duration of life. n Remar.
Bilo. after- Jeton.

Grams. Gram.
284 1,100 0.200 3 hours........ Less than 20 hours... Gluteal... White and brown female.
286 1,315 .1977 2 hours........ Survived............. ..do....... White and black female
285 1,385 .200 Present....... do................ ...do....... Yellow and white female.
287 1,140 .210 15 minutes.... 25 minutes.......... ...do....... Grayfemale.

SERIES B.

307 1,175 0.136 5 hours....... 6 hours, 20 minutes... Lumbar... Gray female.
306 1,860 .134 3 hours........ 4 hours...... ... do....... o.
181 1, 230 .130 4 hours........ 5 hours .............. do...... Gray.

SERIES C.

425 1,520 0.131 1 hour......... Survived............. Lumbar... Gray.
426 1,405 .142 30 minutes.... .....do.............. ...do...... Gray female.
427 1,830 .153 50 minutes.........do...................do....... Do.
453 1,160 .200 30 minutes... Less than 20 hours... ..do....... raymale.
455 1,185 .200 .....do....... Survived............ ...do...... rayfemale.
428 1,650 .180 ................ Less than 20 hours......do....... Gramale.
429 1,340 .200 ........... ...... do................ ...do...... Do.

SERIES D.

577 1,380 0.200 10 minut... Less than 18 hours... Glutea.... Gramae.
578 1,670 .210 ....do..... ...... do................ ...do.......o.
579 1,490 .200 15 minutes.... Survived............. ...do...... White and gray male.
580 1,510 .200 ......... ..do................ Lumbar... ra mae
581 1,680 .200 15 minutes.... 50 mlnutes.......... ...do....... Do.
582 1,870 .192 45 mnutes.... Survived............... do ...... Do.


Examination of Table 4 shows that 14 rabbit received from 180 to 210 mg caffein
per kilo. The appearance of symptos in these rabbits varied considerably. In
soe increased reflexes could be noticed in 10 to 15 minutes after the nj ion of
caffein; in others it was delayed 2 or 3 hors. It might be added that the onset of
sympto occurred in many cases very soon after the administrtion of the drug-
on an averae about 10 to 30 minutes after the d was inected. After maller







ACUTE INTOXICATION- ABBITS. 3

s were administered by injection into the lumbar muscles the appearance of
ymptoms was delayed several hours in some cases. The duration of life in these 14
rabbits varied considerably. Eight of them died within 1 to 20 hours; six survived.
About 0.2 gram caffein per kilo may be regarded as the minimum fatal dose, while
the minimum toxic dose is somewhere between 130 and 150 mg per kilo.

INTRAVENOUS INJECTION.
These experiments were carried out on well-fed, full-grown gray rabbits. The diet
for several days preceding the experiments consisted of oats or carrots, which were given
ad libitum. The injections were made into the ear veins from a burette or by means
of a syringe, the temperature of the caffein solution being about 400 C. Attention
was also directed to the effect of the rate of injection and of the concentration on the
toxicity. The minimum toxic as well as lethal doses were determined as shown in
the following experiments.
SERIES A.
In these experiments the rate of injection was about 1 cc of 2 per cent caffein solution
per minute.
Rabbit 194. White, female. Weight, 1,310 grams.
October 19: Injected 7.5 cc 2 per cent solution caffein (115 mg per kilo) into the ear
vein. Rabbit showed stiffness; paralysis of extremities appeared soon after.a Rabbit
survived.
Rabbit 56. Gray, female. Weight, 1,635 grams.
January 31: 2 p. m., 11 cc 2 per cent caffein (134 mg per kilo) injected into ear vein,
in about 11 minutes 2.10 p. m., convulsions, rabbit remained lying on its side; during
the rest of the hour it had convulsions occasionally; 3.20 p. m., convulsions and died.
Rabbit did not urinate after the injection of caffein.
Rabbit 557. Gray, female. Weight, 1,580 grams.
January 31: 2.30 to 2.37 p. m., 7 cc 2 per cent caffein injected from the burette at
the rate of 1 cc per minute; 2.37 p. m., fow of liquid ceased, veins were engorged and
bled freely, injection was continued by means of a syringe; 2 cc 2 per cent caffein
inected in two minutes; injections discontinued as convulsions appeared; 2.50 p. .,
ra bit raised itself but fell over; 3.10 p. m., rabbit assumed normal attitude, walked
about the floor without manifesting any signs of the effects of caffein; 4.30 p. m.,
walked about, gait normal, condition seemed to be good.
February 1: 2 p. i., condition good, appetite good, total amount of caffein injected,
9 cc 2 per cent solution, or 114 mg per kilo.
Rabbit 558. Gray, female. Weight, 1,590 grams.
January 31: 3 p. m., given 8 cc 2 per cent caffein in eight minutes; 3.10 p. n.,
violent convulsions; 3.20 p. m., rabbit was stretched out on his abdomen, extremities
extended, urinated; 4.30 p. ni., looked normal; was able to walk about.
February 1: 2 p. m., condition good, appetite good.
Rabbit 92. Belgian hare t,ale eight,1,770 grams.
February 18: 4.26 to 4.39 p. m., 12.5 cc warm caffin solution (0.141 gram per kilo)
injected into er vein, convulsion followed when this quantity was injcted, tonic
rigidity of limbs followed soon after; 4.52 p. m., condition unchang, rabbit on floor,
limbs tretched out, and lying on abdomen.
Rabbit 94. Belgian hare, female. eight, 1,350 grams. Carrot diet for about 10 da
before the experiment.
February 19: 12.20 p. m., 5 cc 2 per cent caffein (74 mg per kilo) injected into
earvein in five minutes, edema of the ear other ear sed 3.5 cc injected in 10 min-
utes, repeated convulsions; 1.25 p. n., rabbit still alive, frequent attacks of convul-
sions; 2.30p. ., found dead Total amount injected in 15 inutes, 8.5 cc, or 0.126
gram per kilo.
It will be observed in the preceding experiments that symptoms of evere intoxi-
cation were present in all of the six rabbit, but only two of these (Nos. 29 and 556)
died from the effects of caffein. Of those which survived, three r ived dos of
a Time of Injection inadvertently omitted, but wa probably not slower than In the other cases of this
series.






8 THE TOXICITY OF CAFFEI

100 to 114 mg caffein per kilo, and another (No. 292) received 141 p
kilo. The deat of rabbits Nos. 294 and 56 may be of
exceptionally low resistance to caffein.
SERIEs B.
Doses of 160 to 200 mg caffein per kilo were employed in these experiments. The
rate of injection was 1 cc per minute, with the exception of Experiment 24, in
which 10.8 cc 2 per cent caffein were introduced in 17 minutes and 25 seconds
Rabbit 562. Gray female. Weight, 1,650 grams. Diet, oats.
February 1: Injection began at 3 p. m., injected 10 cc in 12 minutes; 301 .
to 3.09 p. m., 3 cc injected, convulsions; 3.09 p. m. to 3.14 p. m., 3 c injecte fol-
lowed by violent convulsions, marked opisthotonos; 4.30 p. m., rabbit died; total
quantity injected, 16 cc.
Rabbit 561. Gray female. Weight, 1,450 grams. Diet, oats.
February 1: Injection began at 11.40 a. nm.; 11.48, rabbit truggled, 7 cc 2 per cent
caffein injected; 11.50, convulsions, 10 cc 2 per cent caffein total amount injected;
11.55 a. m., injections stopped; injections resumed 11.58, violent convulsions, injec-
tions discontinued, total quantity received, 14.5 cc 2 per cent caffein solution; 1.30
p. m., found dead, did not urinate, 25 cc urine found in the bladder.
Rabbit 560. Gray male. Weight, 1,620 grams. Diet, oats.
February 1: Injection began 11 a. m.; 11.10 a. m., 7 cc 2 per ct caffein injected
rabbit struggled; 1 cc was injected during the next three minutes, rabbit struggled
but there were no convulsions, injection stopped; resumed at 11.15 a. and
continued 10 minutes, 8 cc 2 per cent caffein introduced during this time; total
amount caffein injected, 16 cc; reflexes markedly increased; n, teta con-
vulsions off and on until 2 p. m., then remained stretched out on extremi-
ties extended.
February 2: 9 a. m., found dead.
Rabbit 559. Gray female. Weight, 1,875 grams. Diet oats.
January 31: 4 p. m., convulsions after injection of 9 cc 2 per cent caffein in 14
minutes; 4.08 p. m., convulsions after injection of 7 cc caffein in 8 inue; 4.10 to
4.12 p. m:, injected 2 cc more, rabbit lying stretched out on abdomen, ex
extended; total amount of caffein injected, 18 cc (190 mg per kilo).
February 1: 2 p. m., condition good, walked about, appetite good, passed 155 c
dark, reddish-brown urine since 5.30 p. m. previous day.
Rabbit 279. Gray and white female. Weight, 1,320 grams.
February 24: 10.09 a. m., 6 cc 2 per cent caffein passed rapidly into jugul vein;
10.15 a. m., involuntary twitching of muscles of legs, but no other symptom; 0.
to 10.26, 3 cc of 2 per cent caffein injected; 10.27 to 10.28, 2 cc 2 per cent caffein
injected, convulsions; 10.29, convulsions stopped; 10.32, convulsions; 11 a. m., rab-
bit lying on its side, anterior extremities paralyzed, posterior extremities contracted,
no clonic convulsions, breathed deeper and more slowly than normal 1110 a. m.,
rabbit died, had no convulsions immediately before death; amount of cafein injected,
11 cc 2 per cent solution, or 0.166 gram per kilo.
Rabbit 254. Belgian hare, female. eight, 1,285 grams. Diet, oats.
November 12: 1.30J to 1.47j p. m., received 10.8 cc 2 per cent caffein from burette
into ear vein, after injection of 6.2 cc dyspnaa, 6.7 cc struggling, convulsions; at
1.501 p. m., released from holder, paralysis specially marked in the anterior extremi-
ties; 1.50 p. m., recovered, survived; total ount injected 108 cc 2 per cent
caffein in 17 minutes and 25 seconds, or 0.16 gr caffein per kilo
Rabbit 255. Belgian hare, male. Weight, 1,105 grams Diet oats.
November 12: 2.31j to 2.354 p. m., received 3.7 cc; from 2.37 to 2. p. .,
injected; after injection of 6.1 cc convulsions followed by dyp cont-
uous struggling; when 8.3 cc were injcted rabbit had another convulsion; 47 pm.
tonic contractio of anterior extremities; amount injected, 8.7 cc (18 mg per kilo)
in 15 minutes ad 35 seconds:
Rabbit 57. Grayfeale. Diet, oats.
February 6: Injection began at 4.11 p. m.; 4.18, convulions after injection of
5 ce 2 per cent caffein; 4.21, convulsion aer total injection of 8 cc; 4.24 p. m., nje
ion resumed and 2 cc more introduced; 4.28 p. m., convulions, injected 2 cc more;
tot caffein injected, 12 c, or 162 g per kilo; 4.40 p. m., rabbit palyed in po
teor extremities 5 p. ., found dead.






ACUTE INTOXICATION-RABBITS. 39

In the eight experiment comprising series B rabbits Nos. 567, 254, 279, and 255,
w h may be designated as Group II, received doses of 162, 160, 166, and 158 mg,
respectively. Nos. 562, 561, 560, and 559, which may be designated as Group I,
receivd about 200 mg affein per kilo. In Group II, which received the smaller
dses, one (No, 254) survived. This may be regarded as exceptional, since, as was
shown in the experiments of the preceding series, even smaller doses may be fatal.
About 10 mg per kilo is, therefore, the smallest surely fatal dose. This might be
arded as a contradiction of the results obtained for rabbit No. 559, but it will be
noticed that in this case diuresis was very marked. The results of experiment
Nos 294 and 255 are of interest in this connection, since they indicate tat a moderate
dierence in the rate of injection is without any effect on the toxicity of caffein.
The greater resistance to caffein of rabbit No. 559 is in all probability due, therefore,
to increased diuresis.
SERIES C.
In these experiments the minimum toxic dose was determined. The conditions
were the as in the experiments of the other series.
Rabbit 3. Belgian hare, female. Weight, 1,610 grams. Diet, oats.
February 18: 3.40 to 3.43 p. m., 4 cc 2 per cent warm caffein solution injected into
ear vein convulsions when 3 cc were injected, repeated attacks; 4 p. m., raised itself
on e, but fell over immediately and lay stretched on abdomen.
February 19: 9 a. m., rabbit looked normal, apparently recovered.
Rabbit 27. White male. Weight, 2,30 grams.
October 26: 3.291 to 3.371 p. m., injected into ear from burette 6.7 cc 2 per cent
caffein, no symptoms; experiment discontinued; survived.
Rabbit 563. Gray feale. eight, 1,650 grams. Diet, oats.
February 6: Injection bean at 1.02 p. m., injected 3.5 cc 2 per cent caffein (42
per kilo) in four minutes, 0.6 cc more within the next two and one-half minutes, total
amount injected 4.1 cc; 1.10 p. m., hypersensitive, some disturbance of muscular
coordination restlessness; 1.35. p m., reflexes decreased, urinated and walked about,
gait normal. Under observation for several days; no symptoms noted.
Rabbit 564. Grayfemale. Weight, 1,515 grams.
February 6: Injection began at 1.26 p. m., 3.5 cc 2 per cent caffein (46 mg per kilo)
injected at the rate of 1 cc per minute; 1.30 p. m., reflexes increased; 1.34 p. m.,
marked paresis of the extremities, rabbit stretched out on abdomen, le abduct(d
and partly extended, able to hop about but gait disturbed, no untoward symp)tos
noticed, under observation for several days after experiment.
Rabbit 565. Gray female. eight, 1,545 grams. Diet, oats.
February 6: Started to inject at 3.40 p. m., received 2.5 cc 2 per cent caffein intra-
y in two minuts or 32 ig per kilo, under observation all afternoon, no
symptoms.
Rabbit 566. Grayfemle. ht, 1,900 ras. Diet oats.
Febary 6: Injection began at 3.05 p. m., received 3 cc 2 per c(et caffein intra-
venously in three inus or 31 g per kilo, no symptoms oberved.
These experiments show that a dose of about 50 ig per kilo when injecte intra-
venously produces mild symptoms, such as increased reflexes. In the four experi-
ment with this aount of caffein these effes were obrv in each cae. In the
experiments in which smaller quantities,30 ing per kilo, were given intravenously
was no anifetation of symptoms. A doe not over 50 mg pr kilo may, there-
o, be regarded as the minimum toxic dse en injected intavenouly uder the
conditions stated.
SRIm8s 1).

A 0.5 per cent caffein solution was used in the experiments in order to test the
t of concentration on i toxicity; the rate of injectn wa I c per inut
Rabbit 569. Gray male. Weight, 1,475 grams. Diet, oats.
Febary 6: 1.50 a. n. t 12.01 p. n., injected 10 c 0.5 per cent caffein; 12.03
to 12.12 ected 10 cc of 0.5 Dr cent caffen 12 .13 to 12.26 p. ., injected






40 THE TOXICITY OF CAFFEIN.

10 cc of 0.5 per cent caffein, total amount injected, 30 cc; 12.20, 35 ccof urine;
12.30, increased reflexes, but no convulsions; 4 p. m., reflexes increased
February 11: Alive, condition good.
Rabbit 574. Gray female. Weight, 1,555 grams. Diet, oats.
February 8: 10.25 to 10.33 a. m., injected 4 cc of 0.5 per cent caffen in salt solution,
injection discontinued for five minutes; 10.38 to 11.10, injected 30 cc, total amount
of caffein solution received, 34 cc; 11.55 a. m., very sensitive; reflexes markedly
increased.
February 9: Alive, condition good.
Rabbit 571. Grayfemale. Weight, 1,530 grams. Diet, oats.
February 7: Injection 3.18 to 3.50 p. m., received 30 cc in 32 minutes, not hyper-
sensitive; 3.55, restlessness and weakness of extremities; 4.10 p. m., control of ante-
rior extremities impaired, distinctly paretic but tried to walk about, died the same
afternoon.
Rabbit 568. Gray male. Weight, 1,605 grams. Diet, oats.
February 7: Injection 10.53 to 11.01 a. m., injected 10 cc 0.5 per cent caffein; 11.03,
injection resumed after two minutes interval; 11.14, received 10 cc 0.5 per cent
caffein intravenously in 11 minutes; 11.16, injection resumed; 11.35, received 12 cc
0.5 per cent caffein, total amount of caffein solution received, 32 cc; 12.30 p. m.,
urinated 14 cc of bloody urine; 12.55 p. m., convulsions and death a few minutes later.
Autopsy showed congestion of viscera, but no other lesions.
Rabbit 570. Gray female. Weight, 1,25 grams. Diet, oats.
February 7: 2.06 to 2.35 p. m., injected 24.5 cc 0.5 per cent caffein, reflexes increased
but no convulsions, paresis especially marked in the anterior extremities; 3 p. m.,
passed urine which was normal in appearance, reflexes not increased but rabbit was
weak.
February 9: Found dead. Autopsy: Liver, spleen, and kidneys congested; large
intestines hemorrhagic; omentum congested and showed the presence of smal caseous
nodules; liver showed adhesion to diaphragm; viscera presented the appearance of
intraabdominal infection.
f Of the five rabbits of this series three died as a result of the administration of caffein.
The other two which survived showed mild symptoms only, such as increased reflexes,
but no evidence of severe poisoning such as was observed after the injection of the
same doses of caffein in series A when a 2 per cent solution of caffein was injected.
Convulsions were noticed in one case only (No. 568); paresis in two cases (Nos. 570
and 571). The nervous symptoms even in this group, therefore, were much milder
than in series A. The percentage of death, however, was greater than in series A, in
which the concentration of caffein was four times as great. It is quite probable that
the strain on the heart due to the sudden increase in volume of the blood and its dilu-
tion might be an important factor in increasing the toxicity of caffein. It is conceiv-
able that doses just sufficiently large to depress the normal heart may cause paralysi
of an already overstrained organ.
SERIEs E.
In the two experiments of this series the rate of injection as a possible factor influ-
encing the toxicity of caffein was tested. A 2 per cent caffein solution was injcted
at the rate of I cc in two and one-half to three minutes.
Rabbit 572. Gray male. Weight, 1,770 grams. Diet, oats.
February 8: Injection began at 3 p. m., discontinued at 3.37 p. m., and resumed at
3.38 p. i.; rabbit was restle; injection finished at 3.52 pm. Total quantity received,
17.4 cc 2 per cent caffin intravenously in 52 minutes; struggled interittentlydring
the injection; anterior legs paralyzed.
February 9: Found dead.
Rabbit 573. Gray male. Weight, 1,810 grams. Diet, oats.
February 8: Started to inject at 1.35 and discontinued at 2.27 p. m.; received 18 cc
2 per cent caffein intravenously in 52 minutes; reflexes markedly in soon
after 2.45, paed bloody urine; 4.30 p. m. reflexes increased; no other symptom.
Feruary 9: 9 a. m., found dead.
It will be observed that some retardation of the onset of symptom was causd by
slower injection, but the final result was the same as when the injections were made







ACUTE INTOXICATIONI-ABBITS. 41

mo rapidly. It is quite probable, therefore, that a much slower rate of injection
may lessen considerably the toxicity of caffein.
From the results of the experiments by intravenous injection summarized in the
ble, ppears that the minimum toxic dose for rabbits of a 2 per cent caffein solu-
tion, injected at the rate of 1 cc per minute, is about 50 mg per kilo. Twice the dose
induces severe symptoms and may be fatal; 160 mg per kilo are surely fatal. If the
rate of injection is diminished, the toxicity of caffein is lessened, but this effect is
ot marked unless the injections are very slow. Dilution of the caffein solution sup-
p to some extent the nervous symptoms, hut the toxicity, on the contrary, seems
to be increased.
TABLE 5.-Intravenous injections.

SERIES A.

Oaffein
o. Weight. per Symptoms. Duration of life. Diet. Remarks.
kilo.

Grams. Mg.
194 1,310 114 Present... Survived................ Oats ..... White female.
55 1,635 134 10 minutes 20 minutes............... ..do..... Gray female.
657 1,580 114 Present... Survived................. ..do...... Do.
558 1,00 100 ...do...........do............. ......... do..... Do.
292 1,770 141 ...do...... ....do ............... ..d.... Do.
194 1,350 126 ...do...... 10 minutes.............. Carrots... Do.

SERIES B, GROUP I.

I62 1,650 200 ........... 1hours.................. Oats...... Gray female.
S 1,450 200 .............. .....do.. ............... do....... o.
560 1,820 200 Present... Less than 24 hours....... ...do...... Do.
559 1,875 190 ...do...... Survived................. do...... Do.


SERIES B, GROUP II.

279 1,320 166 ............ I hour.................. ............ Gray and white female.
264 1,285 160 ............ Survived................. Oats ..... Gray female.
567 .......... 162 ........... About 45 minutes........ ........... Do.
255 .......... 158 ........... Died... .......... .........

SERIES C.

293 1,610 500 Present.. Survived................. Oats..... Gray female.
227 2,320 570 None...... ....do...... ........... White male.
63 1,&60 500 Present .....do................... ...do......Gra female.
564 1,515 460 ...do ........... ................... ...........o.
565 1,45 320 None...... do................... ..do..... Do.
566 1,900 310 ...do ...... .....do................... do...... Do.

SERIES D.

9 1,475 100 Present... Survved................. Oats...... Gray male.
674 1,565 112 ...do...... ..... do ....... ............... do..... fale.
71 1,530 100 ..do...... About 2 ............ ...do..... o
568 1,005 100 ............ 20minutes.............. ...do...... Gray male.
70 1,225 100 ... .....an 20 hours...... 0do ..... bo.


SERIES E.

572 1770 200 Pr nt... About 24 hours.......... Ota......
S73 1,810 200 ... ....... ...... do........ ....... ...do......






42 TOXICITY OF CAFFEIN.

SUMMARY.
The results of the experiments on rabbits show considerable in
of the sinle dose. Individuals differed so widely in theirto
that the same experiments had to be repeated many tes ad-
ministration before satisfactory conclusions could be drawn. This is
illustrated in the experiments by intravenous injection in which a dose of nrly 0.2
gram per kilo was not fatal. Similar instances of exceptionalor of
tiveness to caffein were observed when it was given in other ways. A co
of the toxicity of caffein administered by different methods in this investigation
shows well-marked differences in its activity, although they are not quite so striking
as similar experiments with other alkaloids reported by several observers. The tox-
icity of caffein in these experiments on the rabbit indicates that it is greatest when
given by vein and least when given by mouth. The ratio of the minimum toxic
doses by these two methods of introduction of caffein was about 7.1; the relation of
the minimum fatal dose was about 3.1. The toxicity when given subcutaneously is
about 15 to 20 per cant greater than when given by mouth. The difference between
the intramuscular and subcutaneous injection is even more marked. The toxicity
of caffein when injected into the muscles is about midway between that adminis-
tered by the subcutaneous and intraperitoneal routes, and is about half that injected
intravenously. Meltzer and Auer, 5 who experimented with a number of drugs
found that the intramuscular method of administration is as effective as the intravenous,
fluorescin forming the only exception according to their observations. In the experi-
ments of Sollman and Brown 81 with ergot, the effect was quite different from those
obtained by Meltzer and Auer 68 with the drugs they used. It is quite possible that
the result obtained with ergot is merely illustrative of a difference in the behavior of
various substances in this regard. This appears probable on account of the difference
in the rate of absorption for various substances. Thus, according to Achard, Gaillad,
and Ribot (Compt. rend. Soc. biol., 1907, 62: 90), absorption from the peritoneal
cavity varies with the concentration of the solution and the size of the molecule. The
smaller the molecule and the greater the concentration the more rapid the absorp-
tion. That the rate of absorption from the intramuscular tissues is unequal and
varies for different substances appears from the experiments of eltzer and Auer.
The difference was very striking between intramuscular and subcutaneous adminis-
tration of curara or adrenalin; the results were somewhat different with orphi and
with fluorescin. As shown in their protocols, the onset of the symptoms after the
intramuscular injection of morphin was sooner than after subcutaneous injection,
but in time the difference diminishes and disappears altogether. The absorption of
fluorescin is much faster when the intramuscular path is used than when given sub-
cutaneously, but the writers state that the rate falls far behind that of the intravenous
administration. The difference in toxicity we observed between feeding by mouth
and subcutaneous injection, although distinct, wa not very great. It was much
less than Maurel otained with thehydrobromid of caffein in the rabbit. Whether
this difference between his results and ours is due to the use of the pure alkaloid in
our experiments and the hydrobromid employedby b aurel can not be stated at
present with any deree of accuracy. It is hoped that the work in in the
laboratory will throw some light on the sbject in the near future. But Maurel's
experiments show that various substances behave differently in this regard. Thus
the toxicity of strychnin, he states, is three ties as great when given subcutane-
ously as when given by mouth and six times that of the minimum fatal dose by vein.
It may be rearked, however, that examination of his data shows that hi doses are
much too arge for the rabbit. In experiments with other drugs little or no difference
between the to moe of administration was noticed. Thu, digitalin was but
slightly more active when given subcutaneously than by outh, whi the toxicity
of emtin hydrochlorid was just he sae, whichever one of these of intro






ACUTE INTOXICATION--GINEA PIGS. 43

Sthe substance was used. Differences in the toxicity of substances have also
observed between subcutaneous and intravenous modes of administration,
but here, too, the differences for vaiious substances were unequal.

EXPERIMENTS ON GUINEA PIGS.

The toxicity of affein was studied in a large number of individuals. The experi-
ments were conducted on full-grown anims and were carried out at different seasons
of the year in a variety of ways. Special attention was given to diet as a possible
factor influencing resistance to caffein, and the effect of different modes of adminis-
tration on toxicity. Some animals were therefore fed oats, some carrot, others re-
ceived both hay and oats. Caffein was introduced subcutaneously, intraperitoneally,
by mouth.
SUBCUTANEOUS INJECTION.
SERIES A.

Preliminary experiments carried out on three guinea pigs, which received 360,
300, and 290 ng of caffein per kilo subcutaneously have shown that such does were
rapidly fatal. Two of the animals were seized with convulsions half an hour after
the introduction of caffein and died during the attack. The other had tetanus two
inutes after the injection of caffein. Repeated attacks followed, which teminated
in the death of the animal two and a half hours later. The fatal and toxic doses must
therefore be considerably under 0.3 gram of caffein per kilo when introduced by this
path and smaller doses were therefore injected. The results are shown in the experi-
ments of the next series.
SERIES B.

Experiments with 2 decigrams per kilo constituted this series.
Ginea pig 20. Female. Weight, 497 grams. Dit, oats.
April 2: 5 cc 2 per cent caffein injected subcutaneously at 11.30 a. m.; 1.50 p. m.,
Sof short duration. Died at 3 p. m., three and one-half hours after injection.
Guinea pg 38. Brown male. Weight, 570 grams. Diet, carrots and oats week prevo
to injection.
February 11: 3.50 p. m., 6 cc 2 per cent caffein injected subcutaneoly in back
(10 mg per kilo); 4.15, reflexes increased, ad convulsion of short duration when
disturbed 4.45 p. m., on handling, repeated convulsion and paralysis; 5 p. m., guinea
pig lying on his side, respiratio difficult and labored.
February 11: 5.05 p. m., guinea pig found dead, 2 hours nd 15 minutes after
injection.
Guinea pig 37. Male. ht, 820 grams. Diet, carrot and oats during pr-
ceding the inject ion of ca lfein.
February 11: 3.35 p. m., 8.5 cc 2 per cent caffein injected iubcutaneosly in the
back; p.., ig vey sensitive, anterior extremities paralyze when handled, fr-
quent spasm o ostrior extremities, no symptoms noticed before 5 p. n., although
wathed all the time; 5.05 p. m., guinea pig on iis legs and looked normal. No attack
on handling.
February 12: 9 a. m., found dead; died within18 ho .
Guinea 13. Fale. ght, 618 ra. Di, ots
March 29: 2.45, 6 cc 2 per cent caffein injected s bctaneouly (0.194 gams Ier
March 30: Died at 4 p. ., 25 hours aftr injection.
Guinea pig 36. Male. Weight, 8O0 grams. Fed oats and carrots for one week prerious
to injection.
February 11: 3.30 p. in., 8.5 cc 2 per cent caffein injected sub utaneously into
back; 5 p. ., somew t or sensite than normal, no other symptoms, no elfect
n haldling; 5.5 p. ., no symptos.
February 12: 9 a. n., found dead, about 18 hours after injection.
The results of these experiments, a observed in five inea pig, indicate tht
Stwo deigr of affein per kilo of animal prouce symptoms within a half to about
two and a arter hours after injection. D h follow in two ( ie pig 70 minu






44 THE TOXICITY OF CAFFEIN.

to 1 hour after the first manifestations of symptoms. Two others died during the
night, while one lived 25 hours after the injection of caffein. Even 2 decigram
caffein per kilo weight might therefore be fatal to the guinea pig. Experiments
carried out later have shown, however, that the resistance to caffein is appreciably
greater in some guinea pigs. This is indicated by the following experiments, in hich
doses of 0.2 to 0.24 gram caffein per kilo were administered by the same path.
SERIES C.
Guinea pig 66. Yellow and dark brown male. Weight, 510 grams. Diet, oats.
October 4: 5 cc 2 per cent caffein (0.2 gram per kilo) injected subcutaneously in
the back at 3 p. m.; 5 p. m., no symptoms.
October 5: 9 a. m., alive; condition good.
October 9: Found dead. Autopsy: Congestion of liver, kidney, and small intestine
Guinea pig 65. White and black male. Weight, 510 grams. Diet, oats.
October 4: 5 cc 2 per cent caffein (0.2 gram per kilo) injected subcutaneously in
the back at 3 p. m.; 5 p. m., no symptoms.
October 5: 9 a. m., condition good.
Guinea pig 60. White and gray female. Weight, 320 grams. Diet, oats.
October 3: 2.25 p. m., 3.5 cc 2 per cent caffein ((0.219 gram per kilo) injected sub-
cutaneously in the back; 3.40 p. m., convulsion with recovery; 3.50 p. m., frequent
spasms with paralysis, especially of anterior extremities; 5.30 p. m., tetanus when
removed from cage and put on floor.
October 4: 8.50 a. m., found dead. Autopsy: Congestion of small intestines, lungs,
liver.
Guinea pig 57. White and gray female. Weight, 350 grams. Diet, oats.
October 3: 2.15 p. m., 3.5 cc 2 per cent caffein injected subcutaneously in the back
(0.2 gram per kilo); 3.40 p. m., convulsions with recovery; 5.30 p. m., no marked
symptoms.
October 4: 8.50 a. m., alive, active.
October 6: Found dead at 9 a. m. Autopsy: Congestion of lungs and liver; kidneys
petechiated; severe gastro-enteritis.
Guinea pig 68. Yellow male. Weight, 785 grams. Diet, oats.
October 6: 11.35 a. m., 7.8 cc 2 per cent caffein (0.2 gram per kilo) injected subcu-
taneously; 12 noon, reflexes increased markedly; 4.20 p. m., reflexes the same as at
12 noon.
October 7: 9 a. m., dead. Autopsy: Lungs congested; liver congested and fatty;
spleen congested, kidney showed hemorrhagic spots; gastric ucosa necrotic; small
portion of small intestine inflamed.
Guinea pig 69. White male. Weight, 585 grams. Diet, oats.
October 6: 11.40 a. m., 5.8 cc 2 per cent caffein injected subcutaneously; 12 noon,
reflexes increased, but not as much as in No. 68; 4.20 p. m., guinea pig hypersensitive
reflexes increased more than at 12 noon.
October 7: 9 a. m., alive.
October 15: 9 a. m., found dead.
Guinea pig 61. Brown and black female. Weight, 330 grams. Diet, oats.
October 3: 4 p. m., 4 cc 2 per cent caffein (240 mg per kilo) injected subcutaneously;
5.30 p. ., reflexes increased; runs, but drags posterior extremities.
October 4: 8.50 a. m., found dead.
Guinea pig 62. White, yellow, and black female. Weight, 335 gras. Diet, oats.
October 3: 4.05 p. m., 4 cc 2 per cent caffein (238 g per kilo) njected subu-
taneously in the back; 5 p. m., convulsions; 5.20 p. m., convulsions, alternatngwith
paralysi8 of anterior and posterior extremities.
October 4: 8.50 a. m., found dead.
Guinea pig 70. White and bro male. Weight, 545 gras. Diet, oats
October 7: 3 p. m., 6.5 cc 2 per cent caffein (238 mg per kilo) aqueous soluti
injected subcutaneously; 3.50 p. ., reflexes increased.
October 9: 9 a. m., found dead
Guinea pig 71. Brown and white ma. Weight, 40 ra Dit, oats.
October 7: 3 p. ., 6.5 cc 2 per cent affein solution (0.24 gram per kilo) njected
subcutaneouly; 3.45 p. m., reexes increased, tetanus.
October 9: 9 a. in., found dead.






SACUTE INTOXICATIO UINEA PIGS. 45

ui pg 7. Brown ad white mae. Weght, 560 grams. Diet, oats.
October 7: 3 p. m., 6.5 cc 2 per cent caffein (0.232 gram per kilo) aqueous solution
administered by subcutaneous injection; 3.35 p. m., reflexes increased.
October 10: found dead. Autopsy: Nos. 70, 71, 72 showed congestion of organs.
The reaction to caffein in the experiments of this series (C) showed considerable
variation. The appearance of symptoms, as well as the final outcome of the experi-
ent, differed markedly in a number of cases, notwithstanding the fact that the
conditions were the same; thus the administration of 0.2 gram per kilo to guinea
pigs, all of which received the same diet, induced no symptoms in two of the animals
(Nos. 66 and 65), while marked symptoms were observed in the other four; in two
of these the symptoms appeared in one hour and a quarter after injection, and in two
others (Nos. 68 and 69), mild symptoms only appeared in 20 or 25 minutes. The
last two were under observation for 4 hours longer, but there was no visible change
in their condition. The duration of life in all of these guinea pigs, as indicated in
the table, likewise varied. Two (Nos. 60 and 68) died during the night after they
received caffein, one survived (No. 65), and three others (Nos. 57, 66, and 69) lived
21, 5, and 9 days, respectively. Experiments with larger doses likewise showed
differences in the behavior of these animals toward caffein, but they were not quite
so marked. As shown in the table, symptoms appeared in from 35 minutes to 1.5 hours
after injection. The duration of life was less than 1 day in two pigs, about twice as
long in two others, and in one case between 2 and 3 days.
A comparison made with results obtained in the preceding series shows a striking
difference in the resistance to caffein. As 2 decigrams per kilo proved more rapidly
fatal to the guinea pig than the larger doses employed in the later experiments, this
difference in the resistance to caffein may be due to several factors. As pointed out
in the experiments on rabbits, age might be an important factor influencing the
toxicity of caffein. Unfortunately, no accurate data were available on the age of the
guinea pigs, but they were all apparently full grown, although they differed in weight
considerably. The difference in their ags was in all probability not very great.
Moreover, it will be observed that the resistance in series B and C differed in animals
of approximately the same weight. This is evident on comparing experiments Nos.
20, 3, and 13 of series B with Nos. 65, 66, and 69 of the next series. Again, further
inspection and analysis of these tables show no difference in the toxicity, although
there may be considerable difference in the weight, from which it may be concluded
that the animals were of about the same age or that this plays no part in the resistance
to caffein in the guinea pig.
Diet is another factor which should be taken into consideration in this connection.
The recent work of Hunt indicates that this may influence the resistance of animals
tosoe poisons. Our experiments, however, fail to show any differnce in the toxicity
of the caffein i guinea pigs, whether fed oats, carrots, or both, for different reult were
obtained on the same diet, and there seemed to be little or no difference in the toxicity
of caffein when the diet was different. Other explanations suest themselve to
account for the reul obtained. Seasonal changes hve been assied by a number
of investigators a cause of ariation in the rsistnce to drugs. According to Focke,
frog are more susceptible to digitalis in the spring than in the suner, while Mosch-
kowitsch and Edmunds reported the very opposite results. Schmiedeberg's
obervations on strophatin in fr were in harmony with those of Edmunds lnd
Moschkowitsch." Similar results were reported with guinea pigs. Hlarrington's
experiments indicate that stimulation of the vagus is less effective from Ocber to
anuary than from February to April, when they are also much more ssceptible to
operaive procedure Hunt found that the resistance of guinea pigs to eto tnitril is
about twice as great in te s r months as it is in anuary ad Februar.
Racemigt al be thought of an imortt fator in ths connetion. Since the
uinea is used at different sesons of the year were of several vareties, there i no






46 THE TOXICITY OF C

reason to suppose, however, that the varieties eted in
were more resistant than those used in the winter and spring. It is
therefore, that the greater resistance to caffein of the guinea piof C those
of series B was due to seasonal variation.
Doses of 0.20 to 0.24 gram caffein per kilo weight, therefore, may be as the
minimum fatal dose for the guinea pig, depending upon the season. Since 0.2
per kilo proved to be rapidly fatal in series B, thi quantity was pehap not the
minimum fatal dose for the guinea pig at the season during which the experiments
were made. Additional tests with smaller doses were therefore carried out during
February and March. The results are shown in series D.

SERIES D.
Guinea pig 49. Male. Weight, 510 grams. Diet, oats for 1 previous to eperi-
rment.
March 17: 3 p. m., 4 cc 2 per cent caffein (0.16 gram per kilo) were injected sub-
cutaneously; 4.40 p. m., reflexes increased; 5.40 p. m. no symptoms.
March 18: 9 a. m., found dead, died in less than 18 hours. Autopsy: Hemorrhage
into abdominal cavity; liver and spleen unduly congested; intestines injected;
hemorrhagic area at point of injection.
Guinea pig 40. Male. Weight, 630 grams. Diet, oats and carrots one week previous to
injection.
February 12: 11 a. m., 5 cc 2 per cent caffein (0.158 grm per kilo) injected subcu-
taneously into back.
February 13: 1 p. m., still alive.
February 14: 9 a. m., found dead.
Guinea pig 45. Female. Weight, 435 grams. Diet, oats for about one month previous to
injection.
SMarch 17: 3 p. m., 3.5 cc of 2 per cent caffein injected subcutaneously in the ba
(0.160 gram per kilo); 4.35 p. m., no symptoms; 5.40 p m., no symptoms.
Guinea pig 39. Male. Weight, 820 grams. Diet, oats and carrots.
February 12: 11 a. m., 6 cc (0.15 gram per kilo) 2 per cent affein injected subcu-
taneously in back.
February 14: 9 a. m., alive; seemed to be in good condition; found dead at 1 p. m.
Guinea pig 41. Weight, 660 grams. Diet, oats and carrots one eek previous to in ion
February 12: 11 a. m., 5 cc (0.15 gram per kilo) 2 per cent caffei inected subcu
taneously.
February 14: 2 p. m., pig alive; apparently normal.
February 18: Guinea pig still alive and apparently in good condition.
Guinea pig 46. Female. Weight, 470 grams. Diet, oats about one month previous to
experiment.
March 17: 3.15 p. m., 4 cc (0.170 gram per kilo) 2 per cent caffein injected into back
subcutaneously; 4.35 p. m., reflexes increased, tremors on handling marked; 5.40 p.
m., no change, symptoms about as before.
March 18: 2.30 p. m., no symptoms.
The experiments of this series (D) likewise showed a considerable difference in the
resistance of the individual guinea pigs. Nos. 41, 45, and 46 survived; the rest of
the pigs died within 18 hours to 2 days after the administration of caffein. Since an
autopsy was held on one only, it is impossible to assign a cause for the variation in the
toxicity of caffein in these guinea pig, as the diet and the other conditions under
which the experiments were conducted were the same. It was found in the experi-
ments on cats and rabbits that the presence of morbid processes tends to increase the
toxicity of caffin. The obserations of Ophls are of interest in this connection
He found spontaneous lesions of the kidney ad liver in a large proportion of guinea
pigs examined. The greater usceptibility to caffein of guinea pigs Nos. 39, 40, 9,
is probably due therefore to some pathological hge which increased it toxicity.
About 0.2 to 0.24 gra per kilo my therefore be regarded as the minimum lethal
dose for the normal guinea pig when caffein is introduced subcutaneously, the mii-
mum toxic doe being about 150-10 g per kilo.






ACUTE INTOXICATION GUINEA PIGS. 47

ments were also conducted to determine the largest dose which does not pro-
duce visible effects. In a number of tests with from 100 to 120 mg caffein per
o (series E, see Table 6, p. 51) no manifestation of nervous or muscular disturbance
any parture from the normal in respiratory activity was observed. Such
quantities may be regarded as the largest doses which are surely safe for these animals.
It is qte posible, therefore, that the greater variation in the toxicity of caffein
observed in these experiments is due to morbid conditions. Moreover, there is some
evidence that caffein increases the toxicity of certain poisons, as shown by Hale for
. Is it not posible hat caffein may similarly be affected by poisons cir-
culatig within the body? Indeed the recent work of Loeb makes this supposition
highly probable. This investigator found that caffein and adrenalin injected together
produce myocarditis in the rabbit. It is conceivable that the combined action of
eiand some preexisting poison may cause changes which terminate in the death
of the animal. The delayed death of guinea pigs after the administration of caffein
observed in this and other series may probably be accounted for in this way.
Experiment 57 lends some support to this view. The condition of the kidneys and
the presence of a severe gastro-enteritis are sufficient to account for the death of this
e. Again the frequent association of gastro-enteritis and congestion of the organs
in caffein intoxication found in different animals makes it highly probable that these
lesions were caused by caffein.
INJECTION INTO THE PERITONEAL CAVITY.
The experiments were carried out with different doses. All the guinea pigs in
tssries were kept on a uniform diet, consisting of oats. Most of them were of average
size d there were no wide variations in their weights. The experiments of series A
with the smallest doses were conducted in March and April; all the other experiments
it will be noticed were made in October.
SERIES A.
Guinea pig 41. Weight, 700 grams. Diet, oats.
April 1: 3.30 p. m., 4.5 cc 2 per cent caffein (130 mg per kilo) injected into peri-
tonea cavity. 5.35 p. m., symptoms present but no tetaus.
April 2: Found dead about 2 p. m., duration of life about 22 hours. Autopy:
Subcutaneous hemorrhage at the point of inoculation; serious exudate on visceral
and arietal peritoneum with marked inflammation of peritoneum; portions of
intestes showd slight enteritis.
Guinea pig 49. ale. eght, 370 grams. Diet, oats.
April 1: 3.15 p. n., 2.5 cc 2 per cent caffein (135 mg per kilo) injected into the peri-
toneal cavity; 5.30 p. ., symptoms present; reflexes increaed, but no tetau.
Guinea pig survived.
Guinea pig 47. Female. Weight, 550 grams. Dit, oats sive about Febrr 4.
rch 17: 3.3 p. m., 3.5 cc 2 per cent caffein (127 mg per kilo) injected into pri-
tone avit; 4.3 p. m., increased irritabiity present, but not arked; 5.40 p. m.,
symptoms about the as before.
Marh 18: 2.30 p. m., condition good; no syptos. Suriv.
ea pig 50. Femle. Weight, 290 gras. Diet, oas.
April 1: 3.30 p. m., 2 cc 2 per cent caffein (138 per kilo) injecld into pritoneal
; 5. p. m., sympto preent; reflexes much icreas, but no tetus.
SERIES B.
Guinea pig 51. Yellow female. Weght, 41.5 grams.
October 1: 9.50 a. m., 3 cc (144 mg per kl) 2 per nt caffeinin ito peri-
cavity; 4.30 p. m., no sympto, althugh under oservation all day.
October 3: 2 p. ., alive.
Guina pig St. White male. Weight, 450 grams.
October 1: 9.45 a. m., 3.5 cc, 2 per cent eaffein (155 gn per kilo), injetd into
peritoneal cavity; 4.30 ., no symp de oped since injetion.
October 3: 2 p..,lv.






48 HE T I OF CA

Guinea pig 53. Brown and white male. Weight, 490 grams.
October 1: 9.45 a. m., 4 cc, 2 per cent caffein (163 mg pe kilo), injected ito peri-
toneal cavity; 4.30 p. m., no symptoms developed since injection.
October 3: 2 p. m., alive.
October 8: Found dead. Autopsy: Congestion of lungs, spleen, liver, kidneys, and
small intestines.
SERIES C.
Guinea pig 59. Gray and white. Weight, 375 grams. Diet, oats,
October 3: 2 m. m., 3.75 cc (0.2 gram per kilo) injected into peritoneal cavity; 215
p. m., reflexes increased but not markedly; 4 p. m., reflexes still more increased;
no other symptoms; 5.30 p. m., no symptoms.
October 4: 8.50 a. m., guinea pig alive and active.
Guinea pig 58. Brown and white. Weight, 380 grams. Diet, oats.
October 3: 2 p. m., 3.8 cc caffein (0.2 gram per kilo), 2 per cent solution, injected
into peritoneal cavity; 2.10 p. m., hind legs extended, then tetanus; attack lasted a
few seconds, after which pig raised himself on hi legs, but reflexes remained much
exaggerated; 4 p. m. to 5.30 p. m., no symptoms of caffein intoxication.
October 4: 8.50 a. m., guinea pig alive and active.
Guinea pig 56. Gray and white male. Weight, 440 grams. Diet, oats.
October 1: 11.30 a. m., received 4.6 cc of 2 per cent caffein solution (0.2 m per
kilo) into abdominal cavity; 11.45 a. m., stiffness and rigidity of posterior extremi-
ties, reflexes increased; 12.30 p. m., hind les paralyzed, reflexes increased; 4.35
p. m., no symptoms, guinea pig in good condition.
October 3: Still alive in good condition.
October 14: Died. Autopsy: Anterior lobe of right lung hepatized. Small portion
of small intestine edematous. Other organs normal.
Guinea pig 55. White and yellow male. Weight, 690 grams. Diet, oats.
October 1: 11.30 a. m., received 6.5 cc of 2 per cent solution caffein (188 mg
kilo) into peritoneal cavity; 11.40 a. m. stiffness in all extremities, reflexesmarke
increased; 12.30 p. m., reflexes increased, anterior and posterior extremities paralyzed;
3 p. m., found dead.
SERIES D.
Guinea pig 67. Gray and yellow male. Weight, 330 grams. Diet, oats.
October 5: 11.25 a. m., 4 cc of 2 per cent caffein injected into peritneal cavity
(240 mg per kilo); 11.30 a. m., tetanus-survived, convulsions off and on. Death
at 2.55 p. m. Autopsy: Severe gastroenteritis; kidney petechiated; congestion of
lungs and liver.
Guinea pig 63. Gray and white male. Weight, 340 grams. Diet, oats.
October 5: 11.20 a. m., 4 cc of 2 per cent caffein (235 mg per kilo) injected into
peritoneal cavity.
October 14: Alive and in good condition.
Guinea pig 64. Brown and black female. Weight, 305 grams.
October 5: 11.35 a. m., 3.8 cc 2 per cent solution caffein (250 g per kilo) injted
into peritoneal cavity; 11.40 a. m., tetanus-survived, convulsions off and on, died
at 4.15 p. m. Autopsy: Findings exactly the same as in Np. 67.
Examination of the results of the experiments by intraperitoneal injections showed
that 0.2 gram caffein per kilo was toxic in two guinea pigs (Nos. 59 and 58). Severe
symptos were observed within 15 minutes in No. 56 and within one hour in No.
55 after the administration of approximately the same dose of cafein. One of these
died within three and one-half hous; the other, No. 56, made a good recovery from
the acute effects. This amount of caffein may be regarded, therefore, as he min
mum toxic dose for the guinea pig when injected into the peritoneal cavity. This
is corroborated by the experiments of series B in which smaller doses failed to show
any muscular, nervous, or respiratory syptoms, nor were there any after effects
noticed, as all of them survived ad were kept under observation for some time.
The guinea pigs of series A, however, seem to contradict thes results. It will be
remarked that appreciably smaller doses induced symptoms in all of them, and one
ca te inated fatally. The seasonal variation, already pointed out, is in
probability likewis reonsible for the difference in the resistance between the






ACUTE INTOXCATION-GUINEA PIGS. 49

a ps of series A and B. Tests were made also to determine the minimum
. For this purp the experiments of series D were performed. The
Srs ceof No. 63 in this series is quite striking. W are unable to explain such
a cy in the results obtained under practically uniform conditions. The
minimum fatal dose of caffein, when injected into the peritoneal cavity, is therefore
about 240 to 250 milligrams per kilo. These amounts, it will be observed, were
r y fatal, in contrast to the results obtained when such doses were injected
subcutaneously. This is probably due to a better absorption from the peritoneal
cavity than from the subcutaneous tissues.

ADMINISTRATION BY MOUTH.
Sthe guinea pig in these experiments wre kept on a diet of hay and oats and
were of large size. The tests were made with different doses of caffein in order to
determine the limits of toxicity when the drug was administered by mouth.
G a pig 129. White afd black male. Weight, 855 grams. Diet, oats and hay.
June : 2.20 p. m., 12 cc of 2 per cent caffein (0.28 gram per kilo) by mouth; 3
p. m., refee ; 5 p. m., reflexes still more increased; no other symptoms.
June 7: 9 a. m., found dead; guinea pig passed 75 cc urine, which was almost color-
less. Autopsy: Heart and blood vessels injected; lungs congested; small intestines
congested; other organs apparently normal.
pig 130. Black and bro male. Weight, 800 grams. Diet, oats and hay.
June : 2.30 p. m., 12 cc of 2 per cent caffein (0.3 gram per kilo) administered by
mouth; 3 p. m., reflexes increased; 5 p. m., increase of reflexes greater than at 3
p. m.
Jun 7: 9 a. m., found dead; only a few cubic centimeters of urine passed since
4 p. Auto : Heart and blood vessels injected; lu congested; small intes-
tines congested slightly.
Guinea pig 131. White and yellow male. Weight, 860 grams. Diet, oats and hay.
June 6: 2.40 p. m., 12 cc 2 per cent caffein administered by mouth; 3 p. m., reflexes
inc ; 5 p. m., reflexes still more arkd.
June 7: 9 a. m., found dead, pig passed about 5 cc urine since 4 p. m. of previous day.
Autop Same as in No. 130.
Guinea pig 16. White and black male. ight, 1,000 grams. Diet, oat and y.
e 9: 4 p. m., 7.5 cc 2 per cent caffein solution injected subcutaneously into the
back; 4.50 p. n., reflexes increased.
June 10: 9.30 a. m., moresensiive than normal guinea pigs, but reflexes not quite so
marked as at 5 p. m. previous day, about 15 cc urine passd since caffein wa injected,
reduction of Fehling's solution considerable, no albumin.
June 13: Alive and in ood condition. Appetite good. (NOE.-P llel test with
urine from two guinea pig which did not receive cffein failed to show reduction of
Felling's solution.)
pig 17. White and bron male. Weight, 925 gras. Dt, oas and hay.
June 9: 4 p. m., 7 cc 2 per cent solution caffein injected subcutanously; 4.50 p. m.,
June 10: flexes less marked than at 5 p. m. previous day, but is or sensitive
thnea pig, about 10 cc urine pae since injection of affein, mderate
amount of ruction of Fehling's solution.
June 13: Guinea pig aive, petite good, condition god.
June 16: 9 a. m., found dad.
Guinea pig 15. White and black male. Weight, 9.5.5 grams. Diet, hay and oats.
June 9: 3p. ., 7.5 cc 2 per cent caffein lution given by outh throgh stoach
tube; 4.50 p. i., reflexes increased.
June 10: fexes le than on previous day ad le marked than in No. 136, a few
cubic centimeters dirty brow ne collec but could not be tested for reduction.
June 13: Condition good, appetite good.
16: 9 a. m., found dea.
pig 134. Whi and bow male ight, 740ra Dit, hay and ats
June 9: 2. p. m., 6 c war 2 per cet caffein vuen by mouth thuh
tube; 4.50 p. m., refl increed
1854-Bull. 148-12-4






50 THE TOXICITY OF CAFFIN

June 10: 9.30 a. m., reflexes much less than day before, increase t, a few cubic
centimeters of urine passed since injection of affein, looked brown and dirty, could
not be tested for reducing substances.
June 13: Guinea pig alive, appetite good, condition good.
June 14: 9 a. m., found dead.
Guinea pig 128. White and black male. Weight, 1,075 grams. Diet, hay and oats.
June 7: 10 a. m., 11 cc 2 per cent caffein by mouth through stomach tube; 11.10
a. m., no symptoms, no urine passed; 1 p. m., increased reflexes, about 15 cc (esti-
mated) urine passed; 4 p. m., reflexes increased, still more urine (about cc);
4.50 p. m., tetanus, frequent attacks, then paralysis and death at 4.58 p. m. Autopsy:
Lungs congested; blood vessels of heart injected; intestines slightly congested; fatty
liver.
Guinea pig 126. White and gray male. Weight, 980 grams. Diet, oats and hay.
June 7: 9.40 a. m., 9.8 cc 2 per cent caffein given by mouth through stomach tube;
10 a. m., no symptoms; 11.10 a. m., no urine passed, reflexes increased; 1 p. m., more
sensitive than before; 4 p. m., increase of reflexes more marked, no urine passed; 4.45
p. m., about 15 cc urine collected; 5 p. m., no change.
June 8: 9 a. m., reflexes about the same as 5 p. m. previous day, no urine passed
since 4.45 p. m. previous day, considerable reduction of Fehling's solution, much more
than urine of guinea pig No. 127; 11.05 a. m., convulsions; 12 noon, still alive and
stretched out on abdomen; died at 1 p. m. Autopsy: Lungs badly congested heart
and blood vessels injected; blood vessels of kidney and of small intestines injected;
liver engorged with blood; a few necrotic spots in stomach.
Guinea pig 127. White, black, and brown male. Weight, 760 grams. Diet, oats and hay.
June 7: 9.50 a. m., 7.6 cc 2 per cent caffein by mouth through stomach tube; 10 a. .,
no symptoms; 11.10 a. m., reflexes increased, no urine passed; 1 p. m., very sensitive;
4 p. m., sensitiveness increased, about 20 cc urine passed; .5 p. m., no change.
June 8: 9 a. rn., reflexes about the same as 5 p. m. previous day; 9.30 a. m., guine
pig passed 30 cc urine since he received caffein, urine showed a moderate amount of
reduction; 12 noon, convulsions; died at 2.30 p. m. Autopsy: Lungs congested;
blood vessels of heart and of intestines injected; numerous necrotic spots in stomach;
other organs apparently normal.
Examination of the protocols shows that the absorption of caffein from the gastro-
intestinal canal was quite rapid, symptoms having been observed as early as 20 min-
utes after its introduction. The duration of life, it will be remarked, varied with the
size of the dose. When approximately 3 decigrams per kilo were fed, all the animals
died in the night. They lived, therefore, less than 18 hours. Two decigrams per kilo
were likewise fatal, but the duration of life was longer. To decide whether or not this
is the smallest fatal dose, smaller amounts were fed. It seemed at first that about 150
mg per kilo was the smallest toxic dose, and about 200 per kilo the minimum fatal
dose. Macroscopic examination of the organs, however, threw soe doubt on this
supposition, for well-marked lesions were noticed in all of the guinea pigs which
received 0.2 gram per kilo. It is quite possible, therefore, that the minimum fatal
dose may be somewhat higher, as we have reason to believe that, at least in some patho-
logic conditions, the susceptibility to caffein is increased. The presence of fatty
changes in the liver of No. 128 and the rapid death in th case lends especial support
to this view. Hence, the minimum fatal dose is probably greater than 0.2 gram per
kilo for the normal guinea pig. The doses employed for the testson guinea pigs Ns.
129, 130, and 131 may be considered therefore the minimum fatal dose for theseanials.
It will be also remarked that acroscopical examination of the organs of these nimals
failed to reveal the presence of severe lesion. That the minimum toxic dose is prob-
ably much saller than 0.28 gram per kilo is indicated by the experimen on guinea
pig Nos. 135 and 134, in which 0.15 gam caffein per kilo induce d symptom
in from two tohree hours. Both of these, however, and also No. 137 died four to six
days after the drug was fed. As already pointed ot, caffein may be a factor in the
delayed death of guinea pigs whic recived moderate doses of it. That this suppo-
sition may also be true for guinea pigs Nos. 134, 135, and 137 is indeed made probable
by the observation that after moderate amount of caffein s ptoms may persist in
the guinea pi for about 24 hours, and also by the fact that the secretion of urine in







ACUTE INTOXICATION UINEA PIGS. 51

t e animals was very scanty, as shown in the preceding record of the experiments;
this slow elimination of caffein and its products of decomposition. It is con-
ceivable that the presence of toxic amounts of caffein in the body for a considerable
length of me would induce changes that ultimately lead to the death of the animal
or that morbid processes are set up by the combined action of caffein and some pre-
existing poison. Since some guinea pigs, however, survived the doses indicated, it
s more probable that such changes would be brought about by caffein in the presence
of a preexisting poison. The death of these pigs, and also of No. 137 several days later,
is difficult to account for on any other theory than the one suggested. Were it not for
he fact that controls, that is, animals of the same lot which had not received caffein
survived all of the experimental animals, changed conditions of environment or acci-
dent might be considered the cause of death in the guinea pigs of the last series.

TABLE 6.-Subcutaneous injection of guinea pigs.
SERIES A.

Num- CaIein
er of per mpta eofm Duration of life. Diet. Month. Remarks.
pig. kilo. symptoms.

Grams. Gram.
18 500 0.300 2 minutes.......... 2 hours 40 minutes.. Carrots...... March..... Female.
15 548 .290 .................... 30 minutes......... Oats........ ..do....... Do.
14 442 .360 15 minutes.... ...... do............. ..do....... ...do....... Do.

SERIES B.

20 97 0.200 2hours0 minutes. 3 hours 30 minutes.. Oats........ April...... Female.
38 570 .210 25 minutes........ 2 hours 15 minutes.. Carrots..... February Male.
37 820 .200 1 hour 25 minutes.. Less than 18 hours.. Carrots and ...do....... Do.
oats.
113 618 .194 .................2. 25hours...... Oats........ March....Female
S 850 .200 hour 30 minutes.. 18 hours............. Carrots and February. Male.
oats.

SERIES C.

66 510 0.200 None............ days............... Oats....... October.. Male.
65 510 .200 .....do.............. Survived.................do......... ..do...... Do.
60 320 .219 1 hour 15 minutes.. Within 18 hours........do........ do...... Female.
57 350 .200 .....do............. About 2 days ....... .....do ....... .do....... Do.
68 785 .200 25 minutes........ Less than 22 hours. .....do....... do....... Male.
09 585 .200 20 minutes........ 9 days..................do....... ..do....... Do.
1 330 .240 1 hour 30 minute.. Less than 24 hours.. .....do........ ...do.,,.. Female.
2 335 .238 1hour... ...... .... do ..... ...... .....do....... ..do....... D1o.
70 4 .238 50 minutes.......... About 2 days...... ....do... ..... do....... Mae
71 540 .240 45 minute .................. do.......do .......do..........do do....... Do.
72 5W .232 35 minutes......... About 3 days,..... .....do..........do....... Do.

SERIES D.

49 510 0. 1 1 hour minutes.. Le thanl8 hoiurs.. Oats........ Mrh.... Male.
40 0 .158 .................. Less than 2 days... Oats a nd Februar Do.
carrots.
45 3 .10 N............... .... Su ved........... Oat ... Marc... Female
39 820 .150 ................... 2days ............... Oats a n d February. Male.
earrots.
1 66 .1 .................... i .................do ..... .. .....
46 470 .170 hour 20 minutes..... do............... Oats ().. Mar... Female

SERIES E.

19 0.100 ................... Surv ed........... Oats ........ April......
42 490 .120 None.............. ...do. ... .....do....... ebruary
43 430 .116 .....do ... ........... .....do.......... ....do. ... ...do......
44 535 .112 ..... do .............. .....do............... .... do....... ...do......
97 330 .100 .....do............. .....do(o............. .....do....... Novemter
98 20 .100 .....do............. About3days...... Carrot..... ...do.....







52 THE TOXICITY OF CAFFEIN.

TABE 7.-Injeci into peritonea cavity; g

SERIES A.

Num- Caffein
ber of Weight. perpa e of Duration of life. Diet. Moth.
pig. kilo. Pto

Grams. Gram.
41 700 0.130 2hours............ 22 hours............. Oats........ April...... Male
49 370 .135 2 hours 15 minutes. Survived............. ............. ..do....... Do.
47 550 .127 1 hour..... ..... ...do........... ..... do...... March.... Female.
50 290 .138 2 hours............ ...do............. ...do....... April...... Do.

SERIES B.

51 415 0.144 None ............ Survived............ Oats....... October... Female.
52 450 .155 .....do............. ....do.............. do.. ..do....... Male.
53 490 .163 ....do............. .....do.................do........do....... Do.

SERIES C.

59 375 0.200 15 minutes......... Survived........... Oats........ October.. Graand
white.
58 380 .20 10 minutes......... .....do ................ ....do....... ...,~.......
56 440 .200 15 minutes....... 14 days ............. ....do....... ...do....... Male.
55 690 .188 1 hour............. 3 hours 30 minutes. .....do....... ...do....... Do.

SERIES D.

67 330 0.240 5 minutes.......... 30 minutes......... Oats........ October... Male
63 340 .235 .................... Survived............ do.........do....... Do.
64 305 .250 25 minutes......... 4 hours 40 inutes... .......... do..... Female.


TABLE 8.-Caffein by mouth; guinea pigs.

SERIES J.

Num- Caffein Appeane of
ber o Weight. per Appe c ofm Duration of life. Diet. Month. Remarks.
pig. kilo. symptoms.

Grams. Gram.
129 855 0.280 40 minutes.........Less tan 8 hours... 1ay andoa June...... Male.
130 800 .300 30 minutes....... Less than 18 hours.. ..............do.. .. do....... Do.
131 0 .280 20 minutes.. ...... .....do................ ..... do....... ...d ....... Do.
135 955 150 1 hour 50 minutes.. 6 days....................do...... ..do....... Do.
134 740 .110 3 hours .......... 4 days......... ..... ...do....... ...do....... Do.
1 137 925 5 50 minutes......... 6 days.... ......... ...do...... ..do....... Do.
i 136 1,000 150 ..... do .......... Survived..............do.,....... do....... Do.
126 980 .200 20 minutes........ 27 hors........ .. do......... ..do....... Do.
127 760 .200 1 hour ... ........ h ..... ........ .....do....... ...do....... Do.
128 1,075 .200 3 hours............. 7 hours ..... ....do.... ...do..... Do.

SSuuaneous injection for comparison.

SUMMAUY.

A survey of the results obtained in experi nts on guinea pigs shows that the mode
of introduction of affein exerts but litle influence on its toxicity. On careful analy-
sis it will be observed that the rate of absorption after the administration of caffein by
mouth, subcutaneously, or intraperitoneally is about the me for the time of appear-
ance of symptoms. The persistence of the ymptoms of caffein intoxication observed
in these ex riments for 24 hours after administration points to lownation,
which may 1be xpected, owing to the fact hat the guinea pigs b little ine
and eaffein is not diuretic for these animals. The prolonged presenc of caf
in the body probably exerts a harmful influence or after effect, wh h may ac






ACUTE INTOICATION-CATS. 53

for the delayed death of some animals many days after a single dose of caffein was given.
Among the factors which undoubtedly influence toxicity, season should be considered,
while the presence of a diseased condition undoubtedly tends to decrease the resis
f guinea pig to caffein. Diet was without any influence on the toxicity of
the single dose of caffein.
EXPERIMENTS ON CATS.

experiments were performed on well-fed animals which were kept under
observation for several days before the tests with caffein were made. The diet con-
sisted of meat exclusively. In some cases the urine was examined for albumin and
before caffein was given. No tests with caffein were made if large amounts of
were found. It may be remarked that sugar was never found in cats before
the administration of caffein, but that considerable amounts of it were found in some
cases after it was given. Studies by various modes of administration were made, by
subcutaneous injection, inaperitonlly, or by mouth. Attention was also directed
to the resistance to caffein in young cats, several experiments on kittens being made
with this object in view.
SUBCUTANEOUS INJECTION.

Rost stated that caffein is eliminated in the urine unchanged after its introduction
into the body and that the aounts found varied with different species of animals.
In the rabbit the amount eliminted w about 21 per cent; in the dog about 8 per cent;
and in the cat somewhat less than 2.5 per cent. It would appear, therefore, that the
cataffein more readily than the rabbit or dog; its resistance consequently
ought to be greater than that of the other animals. Moderately large doses were accord-
ingly employed in the preliminary experiments (series A), but the results obtained, as
n in te protocols, indicted that cffein is fully as toxic for the cat as for the
rabbit or dog. The doses were then decreased and experiments were performed in
order to ascertain the smallest toxic as well as the smallest fatal dose.
SERUIs A
Three decirams of caffein per kilo were administered in these experiments. The
results are shown in the following protocols:
Cat 4. Black and white. ight, 1,440 grams.
May26: 10.05 a. m., 22 cc 2 per cent caffein (0.3 gram per kilo) inctd subcuta-
neousy; 11.10 a. m., copius saivation, cat irritable muscuar stiffness present, but
no tetanus; 11.45 a. m., cat restless, convulsions, att of short duration, no paralysis
observed after the convulsions, pupils dilated; 4.45 p. m., cat quiet, slight paralsis
present.
May 27: Cat exhausted
May 28: Found dead.
Cat 5. Black and white male. Weight, 1,96 grams.
June 3: 10 a. m., 21 cc of 2 per cent caffein (0.3 gram per ki) injected ubcuta
neously; 12 noon, found dead.
Althere was considerable difference in the duration of life foling the
of the same dose of caffein per kilo, the final outcome was the same, as both
cat died from the effect of the d One died within 2 hours and the other ed
than 30 hours after its administration Three decigrams of caffein per kilo is,
therefore, urely fatal to the animals. Test made with er d are shown in
the following experiments:
SERIES B.
In thee experiments the doses employed ranged between 020 and 0.25 gm caffein
per kilo.






54 THE TXICITY OF CAFFEIN.

Cat 3. Black and whitefemale. Weight, ,854 grams. Well fed.
June 4: 10.30 a. m., 35 cc 2 per cent caffein (0.25 gram per kilo) injected subcuta-
neously; 11 a. m., found dead.
Cat 6. Black and white. Weight, 1,645 grams.
June 3: 20 cc 2 per cent caffein (0.243 gram per kilo) injected subcutaneouly at 3
p. m., cat grew very irritable in a few minutes; about 4. p. reflexes decidedly
increased; 5 p. m., cat paralyzed.
June 4: Cat found dead.
Cat 8. Weight, 1,735 grams.
October 7: 4 p. m., 22 cc 2 per cent caffein (0.25 gam per kilo) injected subcuta-
neously in the back; 4.30 p. m., cat irritable, salivation profuse, convulsions; died at
5.30 p. m.; no urine passed after caffein was given.
Cat 9. Weight, 1,960 grams.
October 7: 3.45 p. m., 25 cc 2 per cent caffein (0.25 gram per kilo) injected subcuta-
neously in the back; 4.45 p. m., cat very irritable, repeated attacks of convulsions,
salivation copious; died at 5.30 p. m.; cat did not urinate after injection of caffein.
Cat 12. Striped kitten. Weight, 1,185 grams.
October 9: Urine examined, no albumin, no sugar; 1.45 p. m., 12 cc 2 per cent
caffein administered; 5 p. m., cat alive, no symptoms except salivation an general
irritability.
October 10: 10.30 a. m., found dead. About 15 cc urine collected, but no examina-
tion made.
Cat 14. Black. Weight, 1,855 grams.
October 8: 1.40 p. m., 18.5 cc 2 per cent caffein (0.2 gram per klo); 3 p. m., cat
became restless about 10 minutes after caffein was injected; cried persistently and
moved about in cage, no convulsions, cat urinated about 15 cc, cat defecated.
October 9: 9 a. m., cat found dead in cage. Urine gave very heavy reduction of
Fehling's solution (much more than was obtained from urine of rabbits); 20 cc urine
analyzed contained 4.65 per cent sugar. Autopsy: Lungs deeply congested; liver
marked fatty infiltration and degeneration; spleen normal; kidneys pale and anemic;
intestines normal; stomach normal.
Cat 15. Striped. Weight, 2,145 grams.
October 8: 2 p. m., 22 cc (0.2 gram per kilo) 2 per cent caffein injected subcutane-
ously; 2.30 p. m., cat irritable, restless, trying to get out of cage, crying persistently;
2.40, convulsions lasting about two minutes, then cat raised itself and made attempts
to get out of cage, no salivation, cat urinated about 10 cc and defecated.
October 9: 9 a. m., cat found dead in cage, about 10 cc of urine contained enormous
quantities of sugar. Autopsy: Lungs severely congested; liver showed marked fatty
degeneration; spleen normal; kidneys slightly pale and anemic; intestines mildly con-
gested; stomach normal.
Cat 19. White. Weight, 1,100 grams.
October 20: 13 cc of 2 per cent caffein (0.236 gram per kilo). About 15 minutes
later cat became irritable, reflexes increased, persistent crying, stiffness of extremities
diarrhea present; 4.30 p. m., stiffness of muscles, coordination much disturbed walke
with great difficulty; 4.30 p. m., no new symptoms, persistent crying continued.
October 21: Found dead.
Cat 20. White kitten. Weight, 790 grams.
October 20: 11.35 a. m., 10 cc 2 per cent caffein (0.25 gram per kilo) ivensubcu-
taneously; 12 noon, convulsions followed by paralysis; 1.30 p. m., still breathing,
apparently in comatose condition, lay on its side, dyspnoea, pro livaton; 4 p. m.,
convulsions and death.
The results of the experiments of series B show that a dose of even 0.2 caffein per kilo
is very toxic for the cat. Symptoms appeaed in one animal 40 minutes after the inje-
tionofcaffein. Some of them were found dead 18 hours afterinjection, which eansthat
the duration of life was probably a great deal less since there was evidence that they
had been dead for some time. Death occurred quite sn after larger doses were
injected. Cat No. 3 died 30 minutes after it received caffein. The amounts employed
in these experiments can not be considered therefore as the inimu fatal doses.
Saller doses were then tri, as shown in the exprints of the next seri.






ACUTE INTOXICATION-CATS. 55

SERIES C.

Experiments were performed on five cats which received from 140 to 155 mg per kilo,
as follows:
Cat 24. Striped. Weight, 1,300 grams.
October 25: 10 a. ., 0 cc urine, albumin moderate amount-no sugar; 10 cc caffein
injected subcutaneously at 12 noon; 12.30, irritable, cried persistently, no appetite;
4 p. m., no convulsions, but persistent crying.
October 27: Cat was still alive.
Cat 17. Weight, ,620 grams.
ctober 12: 9.30 a. m., 65 cc urine collected; more than a trace of albumin present,
no reduction of Fehling's solution; 3 p. m., 20 cc 2 per cent caffein (150 mg per kilo)
injected subcutaneously; 3.15 p. m., irritable and restless.
October 13: 9 a. m., about 15 cc urine collected, reduction of Fehling's solution
marked; osazone test also positive.
Cat 3. Black and white. Weight, 1,645 grams.
October 25: 10 a. m., 140 cc urine collected (since October 23), small amount of
albumin present, no sugar.
October 27: 9 a. m., no albumin; no sugarin urine; 11.50 a. m., 12.5 cc caffein injected
subcutaneously (0.15 gram per kilo); 1 p. m., convulsions and death.
Cat 7. Striped kitten. Weight, 1,285 grams.
October 11: Urine collected, no albumin, no sugar; 9.50 a. m., 10 cc 2 per cent caf-
fein injected subcutaneously in the back; 10.10, violent convulsions lasting about 30
seconds; 10.20, convulsions of shorter duration; 10.30 convulsions; 10.35, convulsions
lasg a few seconds; urine passed about 10.20, contained a moderate amount of albu-
min, but there was no reduction of Fehling's solution; 10.45, profuse salivation and
palysis; died about 10.50.
Cat 39. Yellow. Weight, 2,285 grams.
April 13: 2.40 p. m., 16 cc 2 per cent caffein (0.14 gram per kilo) injected subcu-
teouslyin the back; 3.45 p. m., cat died.
Of the five experiments of this series three died after doses of 140, 150, and 155 mg
per kilo. The other two showed symptoms of toxicity, but survived a dose of 150 mg
per kilo which indicated that the minimum fatal dose was probably reached. To test
this supposition smaller doses were administered, as shown in the following experi-
ments.
SERIES D.

Ten cats were used for this series of experiments, and the doses administered varied
between 103 and 139 mg per kilo. The results shown in the appended table (p. -) in-
dicate thatabout 120 to 140 mg of caffein per kilo may induce mild symptoms in some
cases. The conclusion may be safely drawn therefore that 150 mg per kilo is approxi-
mately the minimum fatal dose for the cat when the drug is given subcutaneously.
That smaller doses are, however, by no means to be regarded as alwayssafe is shown in
the following experiments.
SERIES E.
Cat 4. Weight, 3,25 grams. a
September 14:10.20 a. m., 20 cc 2 per cent caffein 0.12 gra per kilo) injected into
the back; 11 a. m., tetanus and death. Atopsy: congetd; liver coet
and showed hemorrhagic spots in capsules and fatty degeneration; kidneys lightly
congested; other organs normal.
Cat 48. Black feinale. Weight, 3,050 grams.
September 14:18 cc 2 per cent caffin (0.118 gram r kilo) injected sucutanoly
Sthe back; 10.30 a. m., violent con ion and dea. Aop: Lungcongested in
spots showing numerous petechia; liver congested; spleen conigested; other organs
normal.
The diminhed reistance to caffein of cats Nos. 43 and 48 might be due to the
pathologic changes found on autopsy, for eidence is not wanting that the toxicity
at probably old; bad been In the laboratory fr several we before the experiment. Gained in
weight 175 grams.






56 THE TOXI Y CAFFIN.

of drugs might be greatlytered under pathological conditions u has shown
that resistance to acetonitril is considerably diminished in ronic al. This
seems to be true also other drugs under abnormal conditions. es of
atropin78 are required in lead poisoning than under normal conditions to produce
the same results. The following experiment is of interest in this fr in
this case a much smaller dose than was given in experiments Nos 43 and 48 produced
the typical symptoms of caffein poisoning and proved to be fatal.
Cat 47, black and white male. Weight, 4,220 grams.
September 15: Received subcutaneously 18 cc 2 per cent (0.084 gram per
kilo); no symptoms observed for about x ours.
September 16: No symptoms.
September 17: Weight, 4,250 gra ; injected 18 cc 2 per cent in (0.084 gram
per kilo); tetanus and death after two hours. Autops: Severe emorrhagic pnu-
monia; kidneys pale, other organs normal.
Since two controls survived the same dose in proportion to the boy weight of the
animal without showing any symptoms, the assumption is justified that the lower
resistance to caffein was due to the presence of pneumonia, thus affording additional
support to the view that the toxicity of caffein may be increased in disease.

INJECTION INTO THE PERITONEAL CAVITY.
These experiments were carried out -on full-grown and on young subjects. As in
previous experiments, doses of different sizes were employed. A dose of 0.2 gram
per kilo was tried first and then reduced gradually to 0.1 gram per o.
Cat 10. Female. Weight, 2,970 grams.
October 9, 1909: 1.30 p. m., 30 cc 2 per cent caffein (0.2 gram per kilo) injected
into the peritoneal cavity; urine examined for albumin and sugar, negative; cat
found dead at 2.30 p. m. No urine in the bladder.
Cat 16. Black female. Weight, 2,420 grams.
October 9, 1910: Urine examined for albumin and sugar, negative; 2.30 p. m., 22 cc
2 per cent caffein (0.183 gram per kilo) injected into the peritoneal cavity; found
dead at 3 p. m.
Cat 99. Well-fed gray female. Weight, 3 kilos.
June 22, 1911: 3.40 p. m., 15 cc 2 per cent caffein injected into peritoneal cavity;
salivation and marked irritability within one hour after injection.
June 24: Alive, appetite good.
Cat 98. Well-fed black male. Weight, 4,100 grams.
June 22: 3.45 p. m., 20.5 cc 2 er cent caffein (0.1 gram per kilo) injected into
peritoneal cavity; very irritable a few minutes after injection, no other symptoms.
June 24: No symptoms, appetite good.
Cat 93. Black and white. Weight, 1,450 grams.
June 22: 3 p. m., 30 cc 2 per cent caffein (0.137 gram per kilo) injected into pe-
toneal cavity; salivation, no other symptoms; under observation until 6 p. m.
June 23: 9 a. m., no urine, cat showed no symptoms.
June 24: 9 a. m., no symptoms, took nourishment as usual.
Cat 87. Well-fed white female. Weight, 2,615 grams.
June 23: 2.45 p. m., 19 cc 2 per cent caffein (0.145 gram per kilo) injected into peri-
toneal cavity; became irritable and retless.
June 24: 9 a. m., no symptoms, took nourishment s usual.
Cat 97. Gray. Age, 3 months. Weight, 500 gra. Diet, meat
June 24: 2.25 p. m., 5 cc 2 per cent caffein (0.2 gram per kilo) njected nto pe-
toneal cavity; 4 p. m., no symptoms.
June 29: Died
Cat 96. Gray and white. Age, months Weight, 575 grams. Diet meat.
June 24: 2.20 p. m., 4 cc 2 per cnt caffein (0.139 gram per kilo) njected into pe-
toneal cavity; 3.55 p. m., no symptoms.
June 30: ied.
Cat 95. Blak. Age, about 3 months Weight, 860 gras. Diet, eat.
June 24: 10.15 a. m., 8.6 cc 2 per cent cafe inected into peitoneal cavity ali-
vation immediately after injection; 10.25, convulons and paralysis; died 10. a.
Autopsy: Macroscopical examination of the oans, neative.






ACUTE INTOXICATIO ATS. 57

4. Blk and white. Weight, 790 grams. Age, about 3 months. Diet, meat.
June 24: 10 a. m., 8 cc 2 per cent caffein injected into peritoneal cavity; 4 p. m.,
continual observation since injection, cat very irritable, respiration more rapid

Exmination of the above protocols show that a dose of 2 decigrams per kilo was
fatal within one hour to one cat and that a somewhat smaller dose killed another
in 30 minutes. Amounts under 0.15 gram per kilo were just sfficient to
induce mild symptoms, such as increased irritability and salivation, which diap-
Swithin a few hours. In no case were the effects noticeable on the following
day. The experiments on young kittens are especially interesting, as they proved,
con to expectation, to be distinctly more resistant than full grown individuals.
The death of Nos. 97 and 96 within five and six days, respectively, can not be ascribed
to caffein, since some of the controls also died. Moreover, it will be remarked in
this connection that no symptoms appeared in three of the four young kittens after
the administration of a dose which was rapidly fatal to adult cats. The rapid death
of No. 95 after the same dose forms an exception which can not be accounted for, as
macroscopical examination at autopsy proved negative.

ADMINISTRATION BY MOUTH.
Two decigrams per kilo were given at first, but it was found that this amount was
surely fatal The dose was therefore reduced to 0.125 gram per kilo. In all of these
experiments caffein was given by means of a soft rubber catheter slipped over the
stem of a funnel which served as a stomach tube. A 2 per cent aqueous solution was
used throughout these tests except in one case in which caffein was given mixed
with the food..
92 Black and whitefemale. Weight, 1,750 grams.
June 10: 12.05 p. m., 14 cc 2 per cent caffein (0.16 gram per kilo) given by mouth;
cat wa quiet when tied on holder, struggled only a little when tube was put into
stomach; 12.30 p. m., cat vomited, no other symptoms.
June 1: Condition good, appetite good.
Cat 87. Whitemale. Weight, ,620 grams. Diet, meat.
June 5: 2.15 p. m., 20 cc 2 per cent caffein (0.15 gram per kilo) solution admin-
istered by mouth through stomach tube; 2.30 p. m., cat irritable, but no other symp-
to; 5 p. ., condition about the same, except that it was more irritable d showed
some ess of the extremities.
June 13: Alive and in good condition, appetite good, not irritable.
Cat 91. Whitefemale. eight, 3,050 grams.
June10: 12 noon, 23 cc (0.15 gra per kilo) of 2 per cent caffein adinistere by mouth,
cat struggled violently; 1.30, alivation; 1.40 p. m., convulsions; did at 2 p. m.
Autopsy: Congestion of lungs, liver, and spleen; heart vessels injected; other o1ns
normal.
Cat 88. Black and whitefemale. eight, 3,260 grams. Diet, mt.
June : 2.20 p. m., 25 cc of 2 per cent caffein (0.15 gram per kilo given by mouth;
2.45 p. m., cat irritable, no other symptoms (cat did not vomit after the administraion
of cafein); 4 p. m., cat found dead. Autop: Livr very much congested; heart
contracted; body was stll war at the time of autopsy.
Cat 90. White and yellow female. Weight, 2,685 grams. Diet, meat.
June 5: 3.15 p. m., 27 cc of 2 er cent caffein (0.2 per kilo) given by mouth
through stomach tube, about half an hour later cat e irritable and bgn to
alivate; at 4.30 p. m. alivation b came more marked, dyspnwa was well devloped,
and the cat was quite restles and h-a tremors; 5 p. m., short spass of posteior
extremities but lay quietly in the agmost of the tne; 5.20 p. m., convulsions of
shortduration and death, muscular relaxation followed innediately after convulsions,
no voiting, diarhea observed after administration of caffei, ad cat p d about
10 cc of urine.
June 6:9 a. ., found dead.
Cat 89. White and blackeemale. Weight 2,860 grams. Dit, meat.
June 5: 3.15 p. ., 28.6 c (0.2 gra per kilo) of 2 per cent caffein given by mouth
through sto tube, no voiting obsrved, nor any other pto; 330, found
dead Auto : Oran normalver con ted






58 THE TOXICITY OF CAFFEIN.

Cat 82. Gray f ale. March eight 45 grams; June 6, eight 750 Diet,
150 grams of meat daily.
June 7: Given 0.4125 gram of caffein in 150 grams of meat, did not eat.
June 8: Given 0.4125 gram of caffein in 150 grams of meat, refused to eat.
June 9: Given 150 grams of meat without caffein, ate all of it.
June 10: No food given.
June 11: No food given.
June 12: Given 0.4125 gra caffein in 150 grams of meat (150 mg per kilo), ate all
of it.
June 13: Found dead. Autopsy: Lungs congested, liver congested; other organs
apparently normal.
Cat 100. Gray female. Weight, 2,740 grams. Diet, meat.
July 17: 3 p. m., 17 cc of 2 per cent caffein (124 mg per kilo) given by mouth through
stomach tube at 3.20 p. m.; 5 p. m., very irritable, but no other symptoms.
July 18: Under observation all day, no symptoms.
Cat 93. Black and white female. Weight, 1,640 grams.
July 17: 3.30 p. m., 10 cc (0.125 gram per kilo) of 2 per cent caffein given by mouth
through stomach tube.
July 18: Under observation all day, no symptoms.
From the results of the experiments of this series it appears that 0.15 gram caffein
per kilo may be fatal within a few hours after its administration, even if the drug is
mixed with a moderate amount of meat. Experiments 87 and 92 show, however, that
this amount may be borne by some individuals without any serious consequences, as
the cats were under observation for some time after they received caffein, and no
untoward symptoms were noticed in either of them during this time. It may be
remarked that cat No. 92 vomited shortly after it received caffein. It is practically
certain, therefore, that this amount of caffein in proportion to the weight of the animal
will in the great majority of cases prove fatal, and perhaps in a smaller percentage of
individuals it is surely toxic if it does not escape absorption. Smaller doses may
cause irritability in some individuals, but symptoms referable to nervous symptoms
of muscles were absent, as in experiments Nos. 93 and 100. The minimum fatal dose
of caffein for the cat when given by mouth is, therefore, 0.15 gram per kilo.

TABLE 9.-Subcutaneous injection; cats.
SERIES A.

Nim- Weight. Cein Symptoms. Durationoflife.
bet. Wper kilo. hrtoll.

Grams. Gram.
4 1,440 0.30 5 inutes.................................... Over29hours.
5 1,396 .30 ............................................... About 2 hours.

SERIES B.

3 2,84 0. 25 ..................................... ... 3minut.
6 1,645 .243 Few minutes.................................. 1 hou 30 mnutes.
8 1,735 .25 3 minutes................................... I hour.
9 1,960 .25 1hour.............. .................. ....... 1hour 45minuts.
12 1, 18 .20 3 hours. ......................... ... ...... .. 18hours
14 1,55 .20 Ihour 20minutes....... .. ................ Do.
15 2,145 .20 4 m nuts .......................... ..... .. Do.
19 1,100 .236 15 m in es............. ..................... .. Do.
20 790 .25 ...~.... ....... ...... hours 30 m nutes.

SERIES C.

24 1,300 0. 1 1 hour.................... ... ................ Survived.
17 2,60 .15 15 m inutes.................................... Do.
S 1, .15 .................................... ....
7 1,2 155 2o in utes ................................... I hour.
2.28 .14 .......... .... ............ inutes.







ACUT INTOXICATION-CATS. 59

TABLE 9.-Subcutaneous injection; cats-Continued.

SERIES D.


. Weight n Symptoms. Duration of life.
ber- per klo.

Grams. Gram.
13 70 0.139 Restlessness............... .....................
21 1,165 .138 None .... ........ ..... ........... .........
25 965 .103 .....do ......... ................ ........
26 1,60 .125 ....do.........................................
27 1,25 .125 ....do .. ................................
28 2,335 .128 .....do ......................................... Received 2 doses; survived.
40 2,710 .129 .....do ......................................... Do.
41 1,785 .123 .....do.................................. D Do.
42 2,315 .112 .....do........................................... Do.
38 2,325 .120 Mild.......................................... Died after second dose.


SERIES E.1

43 3,225 0.124 ............................................... 40 m inutes.
48 3,050 .118 ................................................ Died soon after.
47 4,220 ........................................... Survived.
'47 4,250 .084 ................................................ 2 hours.

SPathological conditions. s Two days aftr first injection.

TABLE 10.-Injections into peritoneal cavity; cats.

-Caffein
SWeight kil Symptoms. Duration of life.


Grams. Gram.
99 3,000 .100 Mild...................................... Survived.
98 4,100 .100 .....do ........................................ Do.
3 1,450 .137 Very mild .................................... Do.
87 2,615 .145 .....do ........................................ Do.
97 505 .200 None ..................... ............... 5 days.
96 575 .139 .....do......................................... days.
9 8 .200 15 minutes................................... 3 minutes.
4 790 .200 Diarrhea.................................... Survived.
10 2,970 .200 .-......... .............. ........ ......... 1 hour.
16 2,420 .18 .......... .... ............................... 30 m inutes.

1 In few minutes.

TABLE 11.-Administration of caein by mouth; cats.


No. W Symptoms. Durtion of lif.


Grams. Granm.
91 3,050 0.15 1 hour 40 minutes.......................... 2 hors.
88 3, .15 ...................................... hour 4 m uts
92 1,750 .16 25 mnut................................. Surived.
7 2,20 .15 3 hours.................................. Do.
90 2, 5 .20 1 hour 15 minutes ...... ......... ... Lss than 18 hours.
89 2,8 0 .20 .................... .......................... in ute .
82 2,450 .15 ...... ...................................... Les. s than 24 hours.
100 2,740 .124 1 hour 40 m utes ........................... Survived.
9 1, 0 12 .................. ........ .... ............. Do.


SUM MARY.

The toxicity of cffein in cats is sown to b te same when given by mouth
when injected su aneously, the imum fatal dsie in bot ca s ein 0.15
gram per kilo. When intr ced by the intraperiton l route, affein i, on the
co distinctly less toxi. After the admini ion of 0.13 and 0.1 ram






60 THE TOXICITY OF CAFFEIN

caffein per kilo (Nos. 93 and 87) salivation in one cat (No. 93) and irritability and
muscular stiffness in the other were the only effects noticed. These symptom were
no longer observed the next day and the cats appeared to be perfectly norma Experi-
ments with larger doses indicate that the minimum fatal dose by this method of
administration is about 0.2 gram per kilo.

EXPERIMENTS ON DOGS.

The experiments were carried out on well-fed adult dogs and on puppies, kept
under observation for some time before the drug was administerd. Only those
manifesting no signs of abnormality were used for these tests Caffein was given by
mouth mixed with 10 to 20 grams of meat, or subcutaneously in 2 per cent aqueous
solution. The young animals received caffein dissolved in milk. The determination
of the minimum toxic or fatal doses when the drug was fed presented considerable
difficulty, as in many instances the ingestion of the drug was closely followed by
vomiting.
ADMINISTRATION BY MOUTH.
SERIEs A.

The effective dose in these experiments showed considerable variation. One dog
(No. 38) died after a dose of 0.12 gram caffein per kilo, while some subjects survived
doses of 0.2 and 0.23 gram per kilo. In the 12 experiments given in Table 12, page 62,
it will be noticed that from 0.12 to 0.152 gram per kilo proved fatal to three dogs,
while three others survived the same amounts in proportion to the body weight. The
results were the same with larger doses. It may be observed in this connection that
in the case of the five dogs in which vomiting was noticed some time during the 24
hours following the administration of caffein, four survived, No. 38 being the exception.
The greater toxicity of caffein in this case is in all probability due to some morbid
process, the presence of which was indicated by the high temperature of this subject.
That vomiting may avert a fatal issue after larger doses of caffein is made further
probable by experiment on dog No. 48, for which, in the absence of vomiting, a dose of
0.2 gram of caffein per kilo proved fatal. On this supposition the discrepancy in the
results obtained in this series may be readily explained. The smallest doses which
proved fatal in these experiments were 0.145 and 0.152 gram per kilo. No. 38, which
died from a dose of 0.12gram per kilo, may be considered as an exception, as this subject
was not normal. Experiments with caffein on dogs were made at various other times
in this laboratory but failed to show that smaller doses of caffein, even when vomiting
did not occur after its administration, were fatal, although toxic effects were observed.
The conclusion is therefore justified that the minimum fatal dose of caffein for the
normal dog is about 0.15 gram per kilo when given by mouth.

SUBCUTANEOUS INJECTION.
SERIES B.
To deermine the toxicity of caffein more accurately, especially for comparison
with animals of other species, the subcutaneous metho of administration was also
used. The injections were made with a syringe of 20 cc capacity, the contents of
which wore introduced into contiguous areas. The results of experiments on six
dogs indicate that approximately 150 to 160 mg per kilo is the minimum fatal dose,
since such doses proved fatal to two out of the three animals receiving this amount,
while three others which received does of from 143 to 160 mg per lo survived






ACUTE INTOXICATION-DOGS. 61

PERIMENTS ON PUPPIES.
SERIES C.
In th pemets the resistance of young growing puppi to caffein was studied.
Caffein was given by mouth to all the subjects except one, to which it was administered
subcutaneously. The protocols, only a few of which are given, and the tabulated
data of the experiments (p. 62) show that the age of the animal has a decided
influence on the toxicity of caffein.
Do1. W ,1,260 grams.
ugut 2: At 10 a. m. given 12.5 cc of 2 per cent of caffein through stomach tube;
2 p. m., had convulsions, diarrhea, salivation, and stiffness of limbs.
August 3: Found dead 9 a. m. Autopsy: Thoracic viscera apparently normal;
stomach immensely distended and filled with a white, cheesy mass and some fluid;
round worms plentiful in stomach and small intestine; mucosa of entire intestine
congested; contents of lower intestine congested; liver pale; spleen flabby; kidney
congested.
Dog 10. Weight, 1,650 grams.
July 26: 9.30 a. m., 29 cc of 2 per cent caffein added to 60 cc of milk offered, but
refused, and was therefore fed by mouth through stomach tube; 10.25 a. m., no
symptoms; 11.30 a. m., restlessness, extremities stiff, post. extremities spread apart,
g shows well-marked symptoms of caffein poisoning; 12.10 p. m., symptoms more
severe, extremiies extended and spread out, is lying flat on belly so that nose touches
floor of the cage; 12.40 p. ., found dead; was alive at 12.10 p. m. Autopsy: Lungs
showed hemorrhagic foci in all lobes; heart apparently normal; liver fatty; stomach
and intestines filled with round worms; spleen and kidney apparently normal.
Do 9. Weight, 8,000 grams.
July 25: 350 mg caffein per kilo; 5 p. m., lying down most of the time, occaionally
walks about in stall; restlssness present, but not marked; 5.30 p. m., vomit which
looked frothy and mucilaginous noticed on the floor of the stall; no meat particles
noticed in vomit, though searched for; whines occasionally.
July 26: 9 a. m., looks well; no signs of the effect of caffein given the day previous.
Dog 8 Ylow female. Weight, 3,100 grams.
July22: 10.50 a. m., received 1.1 grams of caffein in 10 gras of meat (354 g caffein
per kilo); 3 p. In., vomited mucus; gait clumsy; refused to eat; continually drinking
water; very restless; 4 p. m., convulsions set in at 3.55 p. m.; tonic rigidity of the
posterior extremities; profuse salivation; convulsions were both tonic and clonic in
character, and resembled those seen in rabbit in caffein intoxication; a striking
feature wa the duration of the spasm, which began at 3.55 p. m. and kept up for more
than two hours.
uly : Found ead at 9 a. m.
The data recorded in the table and i the protocols of the experiments of series C
ow that four out of the seven animals experimented upon died in less than 24 hours
after caffin was fed; three of these received 300 to 354 mg caffein per kilo, and one
received 200 g caffein per kilo. No. 8 vomited four hour after caffein was given.
No vomiting was observed in the other three do,. From 0.300 to 0.35 gram of
caffein per kio may be regaded, therefore, s urely fatal to young rowing pppies.
That this is in all probability the minimum lethal dose appears from the following
experiments: No. 9, which received 350 mg per kilo, vomited one hour after and
survived, which indicates that some of it was probably not ab:rbed. The amount
which entered the circultion was therefre less than 350 g pr kilo Since No. 15,
which received 250 mg caffein bcutaneosly, likwis survived, the probabiliti
are that 300 to 350 mg per kilo were the minimum fatal doses for these animals. Moret
over, No. 12, which received 200 mg caffein per kilo, survived, no vomiting having
bee observed. The cse of No. 11, in w hhich te sae amount of caffein in proortio
to body weight proved fatal, may explained raps by the findings of the autopsy.
The result obtained in these experiment justify the conclusion that young rowing
dog ca stand larger dos of caffei than full-rwn and older dog.
Attention may also b called here to the difference in the symptoms produc by
a in ry youn, and n adult dos. It wa ofte noticed in these exeri







62 THE OF C N.

that the symptoms in older subjects when given toxic doses of set in rather
abruptly and ended in instantaneous death. We failed to observe this phenomenon
after the administration of large amounts of caffein to very young dogs, in which tonic
and clonic convulsions alternating with paresis were observed. These symptoms set
in rather gradually and lasted several hours (see experiment No. 8), resembling the
rabbit in this regard.
SUMMARY.

The toxicity of caffein for adult dogs is about the same, whether given by mouth
or injected subcutaneously. The resistance of puppies to caffein is much greater than
that of adults.

TABLE 12.-Administration by mouth; dogs. (Series A.)


No. Weight. ein Results. Remarks.
per kilo.

Kilos. Gram.
47 13.60 0. 144 Survived............. Vomiting observed.
55 12.75 .200 .....do............... Stiffness of muscles; no other symptoms.
56 7.95 .200 Found dead next day..
52 13.60 .147 Survived.............
57 6.50 .230 .....do............... Vomited after 1 hour; convulsions after 1 hour and 45
minutes.
39 23.10 .120 ..do................ Increased frequency of respiration, thirst, loss of appe-
tite, vomited rest of day when he drank water, sali-
vation, restlessness, passed feces frequently.
48 11.50 .174 .....do............. Vomiting observed.
48 12.020200 Found dead next day.. No vomiting observed. Second dose was given 8 day
after first.
54 13.40 .200 Survived............. Vomiting observed.
49 13.15 .152 Found dead next day..
38 14.50 .120 ....do................ Symptoms after hours: Dog had a temperature of
1040 F. before caffein was given; vomited 3 hours
after caffein was fed.
18 10.30 .145 ....do................


TABLE 13.-Subcutaneous injection; dogs. (Series B.)


No. eit. n Results.ark
per kilo.

Kilos. Gram.
62 9.30 0.161 Survived........... Restlessnessand vomiting one-half hour afterinjection
61 A 14.00 .160 Found dead next day..
63 12.00 .150 Survived.......... Restlessness hour after njection.
64 14.00 .150 ...do......... Restlessn and thirst 45 nutes after njection.
59 7.20 160 Died I hour and 20 Marked restlessness, but no convulsion
minutes after injec-
tion.
61 14.60 .143 Survived............. Symptoms observed in 1I hours.


TABLE 14.--Administration by mouth to p pies. (Serie C.)


No. Weight. Caffein Result. Remarks.
Nop. eiigt Resulto


Kilos. ram.
8 3.10 0.354 Found dead next day. Vomited in 4 ours after feeding; restlessness, lo of
a tite, thist, incoordination of muscles, convul-
9 3.15 .350 Survived............. Musular incoordination and stiffness, restlessness,
vomIled 1 hour tcaffein was given.
10 1.60 .350 Died in 3 hours....... Convulsion; no vomiting.
11 1. 26 .00 Found da next ay. Slvation; convulsions.
12 1.28 .200 Survived.......... No symptoms.
15 1.20 .250 ............ ... Subentaneous injction.
16 3.i0 .3 Died in I hour....... Convulons 4 minutes ater caein was ed






CHRONIC INTOXICATION-RABBITS. 63

CHRONIC CAFFEIN INTOXICATION.

The bject of this study was to ascertain the effect of repeated
dosage when caffein was given daily or at longer intervals. The
experiments were tried on rabbits and on dogs. As in the experi-
ments on acute intoxication, the animals were under observation for
some time in the laboratory before the administration of caffein
wa begun in order to ascertain the presence or absence of abnor-
mality. The relation of diet to toxicity received some attention,
but the question was not studied exhaustively in the present inves-
tigation.
EXPERIMENTS ON RABBITS.

Full-grown adult as well as young rabbits were employed. The diet consisted
either of carrots or of oats; water was given ad libitum. The rabbits were kept in
metal cages in a well-lighted and well-ventilated room. Unnecessary handling or
any other procedure tending to fatigue or to cause discomfort to the animals was
very carefully avoided, since we had found that such treatment was likely to decrease
the resistance of the rabbit to caffein. The caffein was administered by feeding by
mouth and through a stomach tube, or by the subcutaneous method. In a good many
cases it was given daily, in some at longer intervals.

SERIEs A.
The experiments of this series formed a preliminary study for the purpose of testing
the effect of moderate doses. One decigram of caffein per kilo was given daily for
several days; when administered at longer intervals the dose was increased to 150 to
200 mg per kilo. It was found that the smaller doses did not produce any symptoms;
even the weights of the animals were not influenced. Doses of medium size given on
two successive days were likewise without any noticeable effect (Nos. 182, 183, 123,
101). When a third dose of this size was given within 48 or 24 hours it proved fatal
(Nos. 123,182, and 183). Exceptionally, however, moderately large doses (for rabbits)
may be given for three consecutive days without fatal issue, as in rabbit No. 101.
When given at intervals of two to three days, larger dose, as may be seen from the
protocols, can be administered without causing cute death (Nos. 173, 181, 201).
The results of the tets of this series point to the absence of any accumulation and
to he possible elimination of moderate doses of caffein and its products of decom-
position within 24 hours or thereabouts. When the doses are larger the time of its
elimination is apparently longer, as shown by the fact that repetitions of the dose the
next day may be fatal, but when a longer interval is allowed it may be given without
causing death. It will be observed that only one rabbit of this seric surived, but
it was extremely emaiated. This condition has bn observed in a number of cases
ter caffein had been given for several days. Even when the dru s withdrawn
th animals continued to lose weight. This may be explained by the condition of
the gastro-intestinal ana as found at autosy. The presnce of inflammation of the
mucous membrane of the stonach and intestins, with uceration of the mucos mem-
brane of the pylorus in one of the rabbits (No. 173) of the series, in all probability
caused diminution or lo of appetite, which of itself wold tend to cause los of fIe
and strength and finally death. Proto of the experiments follow.







64 THE TOXICITY OF CAFFEI

Rabbit 173. Carrots were fed from October 1 to 18 and oats for the rof te experi-
ment.


Date. Weight. C ei Date. eight.


Grams. Gram. Grams. Gram.
Oct. 9........................ 1,980 0.141 Oct. 16 .................... 2,005 0.220
Oct.11...................... 1,905 .190 Oct.18...................... 1,845 ..........
Oct. 13..................... 1,930 .207 Oct. 20....................... 1,740 .230


October 21: Paralysis of posterior extremities.
October 22: 9 a. m., found dead.
The urine was examined before and after the administration of cafein. No symp-
toms were observed after the administration of caffein (5 doses in 11 days), nor w
albumen or sugar found in the urine after any of the experiments on this rabbit.
Autopsy: Pyloric mucosa exhibited several ulcers small intestins showed slight
inflammation; liver deeply congested; kidneys showed marked inflammation of cortex;
other organs practically normal.

Rabbit 181. Diet, carrots September 29-October 17, then oats.

Caffein Caffein
Date. Weight. ei. Date. Weight
per kilo.

Grams. Gram. Gras. Grm
Oct. 4...................... 1,425 0.105 Oct. 11.................... 1370 0.175
Oct. 5..................... 1,450 .100 Oct. 13...................1,385 .180
Oct. 6. ......... ............ 1,270 .100 Oct. 16.................... 1,345 .200
Oct. 7....................... 1,210 .100 Oct. 17..................... 1,030 ..........
Oct. 8.................... 1,375 .130 Oct. 18......... ........... 1,230 ..........
Oct. 9.... .................. 1,305 .153 Oct. 20........... ........ 1,215 ..........


Rabbit was markedly emaciated and weak. No albumen or sugar found in the
urine as a result of caffein feeding.
Rabbit 182. Diet of carrots from September 29.
Received caffein subcutaneously as follows:


ate Wight.C ein Date. Weight.
Dt Weih. per kilo. at. per kilo

Grams. Gram. Grams. Gram.
Oct. 4 ...................... 1,765 0.100 Oct. 8........................ 1, .135
Oct.5........................ 1,880 .100 Oct. 9. .......... .............. ...... .. 150
Oct. 6 ....................... 1,750 .100 Oct. 11....................... 1,05 .174
Oct. 7........................ 1,710 .100


October 12: 11 a. m., 23 hours after caffein was given, convulsions with recovery;
rabbit died at 1.30 p. m. No sugar was found in the urine at any time after the
adminismration of caffein. Albumen was present only in one specimen.
Rabbit 183. D[it of carrots from September 9.
Received caffein subcutaneously as follows:


Date. Weight. Caffein Date. Weight. Cau
per kilo. erkl

Gram. Gram. Grams. Gram.
Oct. 4...................... 1,385 0.100 Oct.8........................ 1,310 0.153
Oct. 5........................ 1,4 .100 Ot.9 ........................ 1,3 0 .14
Oct. 6 .................1,38 .100 Oct. 11 ....................... 1,30 .187
Oct. 7. ...................... 1,122


October 12: 9 a. m., found dead. No albumen was foud in the urine. Only one
ample contained sugar.







CHRONIC INTOXICATION-RA ITS. 65

Rabbit 123. White, female. Diet, oats.
eved caffein subcutaneously as follows:


Date. Weigh. ffein Date. Weight. Caffein
per kilo. per kilo.

Grams. rams. Grams. Grams.
Apr. 14 ....................... 2,350 42 Apr.20....................... 2,126 141
....................... 2,50 90 Apr.21....................... 1 152
r. 7.... ................... 2,325 86 Apr. 22....................... 1,876 160

Rabbit died 30 minutes after last injection of caffein. Autopsy: Stomach exhibited
inflammation of mucosa. Slight enteritis. Liver and kidneys were deeply
cd and dark colored.
Rabit No. 101, white male. Diet, oats.
Received caffein ubutaneously as follows:


Date. Weight. ilo. Date. Weight. perilo.

Grams. Gram. Grams. Gram.
ar ........................ 2,025 0.100 Mar. 24 .................... 1,815 0.166
Mar.19,...... ............. 1,970 .100 Mar. 25............ ...... 1,830 185
S2...... ....... ........... 2,009 .100 Mar.26........................ 1,710 .176
....................... 1,855 .100 Mar. 29 .................... 1,734 .219
Mar. ... ................. 1,738 .114 Apr. 1........................ 1,606 .224


April 5: Found dead. Autopsy: Marked inflammation of gastric mucosa. Con-
siderable enteritis affecting the whole extent of the intestines; liver congested and
friable; kidne deeply congested in cortical and medullary portions; spleen con-
gested, but of norma size; lungs and heart normal.
Four days, 0.1 per kilo; 10 doses in 14 days.
bbit 1. Diet of carrots begun October 1; October 19, oats.
Subcutaneous inections as follows:


Date. Weight. CaffeinDate. Weight. ein
per kilo. Date. Weight. fe

Grams. Gram. Grams. Gram.
Oct ......................... 1,000 0.150 Oct. 16...................... 1 0.
Oct.11 ....... ............ .. 1,015 .180 Oet. 8....................... 850 ..........
Oct.13 .............. ......... 1,065 .187 Oct. 20..................... .. 8"90 .111

Under observation six hours October 20; no s ptoms.
October 23: Died; was much emaciated butdid not show any symptoms; emaciation
set in when caffein was withdrawn; urine never contained sugar or albumen; symp-
tom observed after second dose only.

SERIES B.

The question whether caffein i cumulative in the rabbit, uested in the preceding
experiments, was the ubject of further invstation in Series B. Caffein was given
by outh or subcutaneously. Carrot formed the excluive diet, a measured amount
being given. The rabbits were kept under observation for two weeks, except
No. 370 and 373, records of which were made only for four days before the adinitra-
tin of caffein w begun. affein was given by mouth in experients of Groups I
and II. abbit 292, 293, and 295 received daily 20 cc water by mouth for four days
previous to the administration of caffein, while in the rabbits of Group II the caffein
treatment w preceded by the injection of 0.8 per cent salt solution subcutaneously.
The object in both cass was to ascertain whether or not the methd of the adminis-
tration of caffein has any influence on the animal, but obseration ade m day to
594-Bull 148-12-






66 THE TOXICITY OF CAFFEIN

day failed to show any effect of such treatment. About1 ec of caffein per
kilo was administered daily, with occasional intermissions. Later in the course of
the experiment the doses were increased, 0.15 gram per kilo beingthe maximum dose
given. Rabbit 293 died after the third dose with syptoms of typical caffein poison-
ing. The administration of the same dose of caffein was continued 10 days longer in
Nos. 292 and 295. It was omitted on the seventh, fourteenth, and fifteenth days o
the experiment. On the eighteenth day of the experiment the dose was increased to
150 mg per kilo and was repeated 2 days later. No. 295 was found dead the next
day. No. 292 survived. Rabbits 313 and 315 may be considered together, as they
were treated alike in every respect. The initial dose of 100 mgcaffeiper kilo was
finally increased to 122 mg. After the twelfth dose the emaciation was well marked
and the rabbits were very weak. No. 313 was found dead 2 days, and No. 315
3 days, after the last dose of caffein was given. It should be remarked in this con-
nection that symptoms of caffein poisoning were never observed in these rabbits.
Death was not due, therefore, primarily to caffein, but the rapid loss of flesh and
strength observed during the last few days suggests that it was due to malnutrition
apparently brought about by caffein.
The results obtained by subcutaneous injection of caffein are given in the table
as Group II. The initial dose of 100 mg per kilo was injected daily. No. 298 died
after the second dose. Nos. 223 and 296 received this amount daily for 6 days.
An intermission of 2 days followed, at the end of which the same dose was given
again. The next day it was increased to 150 mg per kilo, but no ffect was observed;
48 hours later this dose was repeated. No. 223 was found dead, but its mate survived.
Symptoms of acute caffein intoxication were not observed in any of these rabbits.
It would seem, therefore, that caffein is not cumulative. This supposition, however,
appears somewhat contradictory in view of the fact that out of the eight rabbits of
this series six died, nor could any cause of death be ascribed other than caffein. Also
the first results of Experiments 293, 370, and 373 might be considered as indicat-
ing that cumulation, though to a moderate extent, does take place, since in these
cases reflexes developed after the drug was given for some time. But this view is
contradicted by the results of Experiment 371, in which 150 mg per kilo given 5
days after the daily dosage of caffein was suspended likewi caused in reflexes.
Cumulation, therefore, does not account for the effects noted in the other rabbit. It
will be observed that rabbit No. 370, as well as Nos. 371 and 373, had diarrhea for
several days. It is quite possible that the weakened condition rendered the rabbi
more sensitive to the action of the drug. This is made highly probable by the ober-
vations recorded in the experiments on acute intoxication with caffein in which
death occurred after small dose. In such cases some pathological condition wa
often disclosed by the autopsy. The results of thi series corroborate, therefore, those
of Series A, and indicate again the absence of cumulative action. The results ob-
tained are in all probability due to malnutrition and other conditions brought about
by congestion of the viscera and consequent injury to the astro-intetinal canal.







CHRONIC ITOXICATION-RABBITS. 67

S16.-Chronic cafein intoxication of rabbits; Seris B on cumulation.


Group I. Group IL Group III.
Data.
No. 292N. o293. No. 295. No. 296. No. 223. No. 298. No. 315. No. 313.

Diet( arotsi 2 days)........ 1,000 1,000 975 30 90 880 355 300
Ca administered (cc) and weight
(grams):
Mar. 5........................... 1,41o ,470' ",s' ",o0 15 ",040" ",, 55 "" 770 770
1,415 1 1,140 1,0 17i
M ar.7............... .............o' "i, i, i,

ar........ 1,350 1,270 1,070 1,000 1,055 1,005 655 665
Mar.1 .......... ........... i.. .......................i' "...' '
1,505 1,46 1,1,2 755 760
ar. ............ ............ 1,580 1, 460 1,230 1,165 1, 170 1,145 730 745
Ma.17............................. 1,5i5 "1,415 i;o, 10 "i8,4' "i,,1 "1,i-' 720 70685
ar. 19 ** *** ***** **** ******** ****2*** ****.** 6****)** -- -
M r 1 ..-. .... ........... ... ......... .. . . .... 7g
........................ 1,565 1,570 1,280 1,195 1,235 1,220 710

21 .7 7 6 ........................ 4 4
.2....................... 1,55 1,530 1,265 1,,215 1.260 755 700
S........7 7 6 (1) (1) (1) 4 4
.................... ...... ,440 1,315 1,175 1,100 1,045 1,150 675 635
Mr. 2.... ... .. ..... 7 7" 6 (1) (1) (1) 4 4
.. 1,335 1, 140 1,110 1145 1,190 1,230 715 700
SM 24 7 ........ 6 (1) (1) (1) 4 4
M ...................... 1.310 (2 1,00 1,115 1,170 1,250 680 650
Mar. 25 7 .... ....... 6 (1) (1) (1) 4 4
S1,375 ........ 1,035 1,125 1,215 1,215 695 685
Mar. 26 7 ....... 6 ........................ 4
1,255........ 1,095 1,105 1,155 1,150 675 696
Mar.27............................. .. ........ ........ ... .. .. .....
7 ........ 6 5.5 6 6 4 4
........................... 1,355 ....... 115 1,120 1,160 1,155 595 685
ar29 7 ........ 6 6 6 5 4 4
.................................. 1,150 1,155 1,165 955 695 675
Mar.30 ,I 7 ........ 6 6 6 ........ 4 4
........................... 1,33 ........ 1,075 1,035 1,095 Dead. 630 610
Mar. ............ 7 ........ 6 6 6 ........ 4 4
1,325 ........ 1,170 1,110 1,140 ........ 690 606
Apr. ........................ 33 ........1, 1,05 1,120 ....... 62 620
Ar 2 ....6........... .... 6 6 6 ........ 4 4
1,390 1,125 1,090 1,155 ....... 695 625
:Apr.3............................ ; -; ;^^^; ;^;^ ;;^^* ;***; **^*; --,- *

Aw 1 7 --.*..i 6 6 6 6 ...... 4 4
Apr. ........................... .. .. ....... ........ ........ ....1,10 1, ........ 55200 .. 0....


Apr......... 7.5 7.5 8...................................
Apr. 5............................ 7 ........ 61,00 ........ S
SAr .1, &0 -5........... 1 ),0410 1,00 1, 110D ..^..... t'^56 5630


9 7.5 7. ........ ........ ........8
Apr. ....................... Sur- ........ D Sr- i .............. D .
vived. vived.

SOn these day 5 c of salt slution was admiistered utaneously
SDead Mar. 23.
*Found dead 9 a. m.

*








68 THE TOXICITY OF CAFFEIN

TABLE 17.-C aniintxication of rabbits, series B, Group IV, on c lation.

RABBIT, 370.

Caffein
Date. Weight. Carrots. Water. Urine. by Symptoms,
stomach.


Mg per
as. Grams. cC. kilo.
Aug. 7............. 2,155 450 50 280 ..........
Aug. 8............. 2,030 450 25 185 ..........
Aug.9 ............. 2,105 290 0 275 ..........
Aug. 10............ 2,095 450 30 335 ..........
Aug. 11.......... 2,105 450 65 360 50
g.12............ 2,125 450 65 220 50
Aug. 13............ 2,120 350 25 265 50
Aug. 14............ 2,170 450 35 275 75
Aug. 15............ 2,175 350 (?) 200 75
Aug.16............ 2,170 360 65 250 75
Aug. 17............ 2,175 310 35 170 100
Aug. 18............ 2,095 180 40 285 100 Severe diarrhea.
Aug. 19............ 2,120 400 (?) 285 125 Do.
Aug. 20............ 2,120 400 (?) 310 125 Better.
Aug. 21............ 2,120 400 70 250 125 Do.
Aug. 22............ 2,040 400 45 265 150 Diarrhea bad.
Aug. 23............ 2,030 370 35 220 150 Darrhea better
Aug. 24............ 1,950 215 40 120 150 Do.
Aug. 25 .......... 1,885 195 35 60 200 Reflexes.
Aug. 26..................... .......... .................... Found dead t 9.


RABBIT, 373.


Aug. 7........... 2,240 450 50 230 ..........
Aug.8........... 2,150 150 30 300 ..........
Aug.9............. 2,120 205 0 150 ..........
Aug.10........ ... 2,150 450 15 245 ..........
Aug. 11........... 2,195 450 5 285 50
Aug. 12............ 2,160 450 65 325 50
Aug. 13........... 2,120 300 45 190 50
Aug. 14............. 2,195 450 40 265 75
Aug.15............ 2,215 350 35 200 75
Aug.16........... 2,205 310 45 225 75
Aug. 17............ 2240 400 40 265 100
Aug. 18........... 2,255 350 30 320 100
Aug. 19............ 2,11 5 (7) 170 125 Severe diarrhea.
Aug. 20........... 2,115 280 35 195 125 Diarrhea better.
Aug. 21............ 2,050 175 75 115 125 Slight diarrhea.
Aug. 22............ 2,00 180 75 130 150
Aug. 23.............. 2,005 200 75 125 150 Reflexes.
Aug. 24............ 1,990 200 75 150 150 Slight diarrhea.
Aug. 25........... 1,950 255 55 132 175 Severeiarrhea.
Aug. 26............ 1,870 205 80 140 None.... Do.
Aug. 27........... 1,830 200 50 140 ...do..... Do.
Aug. 28............ 1,950 400 25 265 ...do.....Slight diarrhea
Aug. 29 ............ 1,825 400 0 315 ...do..... Very weak and In poor condl-
tion.
Aug. 30............ 1,850 .......... 10 140 ...do....
Aug. 31 .......... .. 1 3 .... ................. ...........




....~~~~~~~~~ ~ ~ ~ ~ ~ ~ ~ ......... .. .......... ...







CHRONIC INTOXICATION-RABBITS. 69

S17.-Chronic intoxition of rabbits, series B, Group IV, on cumulation-Contd.

RABBIT, 371.


Date Weigh. Carrots. Water. Urine. Caffein. Symptoms.


IM per
Grams. Grams. ce. kilo.
Aug.7............. 2,240 450 50 300 .........
Aug. 8............. 2,60 450 50 225 ..........
Aug. 9 ............. 2,310 430 (?) 300 ..........
Aug. 10............ 2,295 450 50 305 ..........
Aug. 11............ 2,320 450 50 335 50
Aug. 12 ........... 2,2 450 70 400 50
Aug. 13............ 2,300 350 70 255 50
Aug. 14.......... 2,2 425 55 154 75
Aug15.......... 2, 250 40 125 75
Aug ........... 2,295 155 70 Lost.... 75
Aug. 17 ........... 2,180 105 70 120 100 Severe diarrhea.
Aug. 8............ 2,150 125 70 100 100 Diarrhea better.
Aug. 19............ 2,075 210 (?) 192 100 Diarrhea severe.
Aug. 20............ 2,075 280 70 180 100 Do.
Aug. 21........... 2,165 260 50 225 None.... Diarrhea better.
Aug.22............ 2,105 400 50 275 ...do....
Aug. ............ 2,080 300 0 145 ...do..... Diarrhea severe.
Aug. 24............ 2,105 250 15 245 ...do..... Do.
Aug. 2 ............ 2,055 320 10 176 150 Reflexes.
Aug. 26............ 2,040 190 75 250 150 Died at 1 p. m., without having
showed any symptoms other
than reflexes.


SERIES C.

The subjects used in these experiments were rabbits of medium size and were appar-
ently young or at any rate were not very old. The series was planned for the study
of the possible effect of diet on the toxicity of caffein when given for some time, and
therefore oats were substituted for carrots, which had been fed in the previous work, as
already stated Caffein was given by mouth in the usual way, in 1 per cent solution,
100 g. per ilo daily. Fourteen rabbits were used for these tests. Their weights were
recorded daily and observations made at frequent intervas during the day.
The only change noticed in all of the experiments of this series was progressive loss
of weight which set in from 3 to 8 days after the administration of the drug was begun.
The duration of life varied considerably. No. 382 died after the first dose. No. 389
lived 2 day, No. 386, 3 days, and No. 385, 5 days, No. 390 lived 7 days and No. 404
lived 20 days after the administration of caffein was bQun. The duration of life in all
the others was from 11 to 16 days. The findingataupsy are interesting and sug tive
asregard the possible explanation of the effect of repeated dsae of caffein. In eight
of the rabbi there was involvement of the mucous membrane of the stomach or intes-
ines or of both Since the ane condition of the gstro-intestinal canal was observd
in previous experiments with caffein when injecte subcutaneously, the mre pssing
of the tube into the stomach is obviously not the cause of this condition. The fatal
outcome due is therefore, as was suggested above, to inanition brought about by the
condition of the gstroitestinal canal. Moreover parallel experiment carred out
o rabbit in the s way with alcohol survived this treatment much loner.
Obviously then te passing of the sft rubber cathetr is not the cause of this condition
of thegastro-inteinal al nor th diet. Rabbits wer fed ts sexclusively for several
months in this laboratory and thrived The preence of pneumonia in the other
rabbits of this series way be re arded as accidental, as it is inconceivable that one or
two doses of caffein, as wa the cse in No. 382 and 389, could predis the lun.s to
infection. The rsult of hese experiments therefore are in harmony with tho-e of
the precedng two series, indicating that caffein dos not accumulate in the bod. and
that the toxicity of caffein, whether of the single dos or of re ated dse is the me,







70 THE TOXICITY OF CAFFEIN.

on a diet of carrots or of oats. These results ao show that caffein is more toxic
with repeated dosage. As stated in the historical part of this bul the same view
was held by Gourewitch.Y

Rabbit 386. Belgian female.
Given 1 cc of 1 per cent caffein for each 100 grams, through stomach tube.


Date. Weight. Treat- Date. Weight. Tr
ment. ment.

Grams. cc. Grams. c.
Aug. 17....................... 1,300 13.0 Aug. 19....... ...... .......... () ()
Aug.18..................... 1,215 12.0

August 20: Found dead 9 a. m. Autopsy: Lungs slightly congested; liver engorged
and friable; gall cyst well filled.
Rabbit 389. Black male.
Given 1 cc of 1 per cent caffein for each 100 grams, through stomach tube.


Date. Weight. Treat- Date. Weight
ment.

Grams. c. Grams. ce.
Aug.17....................... 1,070 10.0 Aug. 18..................... 1,025 10.0


August 19: Found dead 9 a. m. Autopsy: Lungs severely congested and partilly
hepatized; liver was engorged; other organs appeared normal.
Rabbit 382. Belgian female.
On August 17 weighed 1,035 grams; received 1 cc of 1 per cent caffein for each 100
grams; 10 cc of 1 per cent caffein given in all.
August 18: Found dead 9 a. m. Autopsy: Lungs congested and hepatized; liver
engorged; stomach showed numerous petechial hemorrhages on mucoa; kidneys
slightly congested; intestines appeared normal.
Rabbit 385. Belgian female.
Given 1 cc of 1 per cent caffein for each 100 grams, through stomach tube.


Date. Weight. Date. Weight. e -
menit,t

Grams. cC. Gram. Cc.
Aug.17.............. 80 A g.20.............. ........ 715 7.0
Aug. 18...................... 760 7.5 Aug.21....................... 700 7.0
Aug. 19....................... 755 7.5

August 22: Found dead 9 a. m. Autopsy: Lungs exhibited pneumonic lesions,
with inflammation of adjacent pleura fibro-plastic exudate present around lung;
liver showed a coccidial infestation; stoach distended with ingeta mucous mem-
brane characterized by a catarrhal inflammation; contents of sall intestine liquid
in nature and bile stained; large inttine soewhat impacted; liver and kidneys
seeminly normal.







CHRONIC INTOXICATION-RABBITS. 71


Given 1 cc 1 per cent caffein for each 100 grams.


Date. Weight. t- Date. Weight. Tret-
ment. ment.

Grams. cC. Grams. cc.
..................... 1,465 14.5 Aug.30...................... 1320 13.0
S.........:......----... 1,475 14.5 Aug. 31 .................. 1,330 13.5
2 n ............................ .......... Sept. 1 ...................... 1,335 13.5
Ag.23-................... 1,475 14.5 Sept. 2..... ............ 1,315 13.0
Aug.4........................ 1,400 14.0 Sept. 3.................... 1,350 13.5
Aug. 5 : .B..................... 1:405 14.0 Sept. 4.................... ... 1,335 13.5
SAug.26---...................... 1,415 14.0 Sept. 5....................... 1,350 13.5
Aug. 27...................... 1,400 14.0 Sept. 6.................... 1,380 14.0
SAu 8............. .... .......... .......... Sept. 7 ..................... 1,375 14.0
....................... 1,310 13.0 Sept.8....................... 1,325 13.0

I Not fed. Reflexes.

September 9: Found dead 9 a. m. Autopsy: Both lungs showed extensive pneu-
mo a, with adhesions to pleura; ~ieuritis and pericarditis very marked; large amount
of ibrous exudate in pleural cavity; pyloric end of stomach slightly congested; liver
congested; other organs normal.
Rabbit 893. Belgian.
Given cc of 1 per cent caffein to each 100 grams, through stomach tube.


Date. Weight. Treat- Date. Weiht. Treat-
ement. meDate. e tt.

Grams. cc. Grams. cc.
Au.17 ....................... 950 9.5 Aug. 25 ..................... 835 8.5
Aug ................... 910 9,0 Aug. 26..................... 780 8.0
Aug.19...................... 895 9.0 Aug.27....................... 765 7.5
S....................... 910 9.0 Aug. 28.................................
S...................... 905 9.0 Aug.29..................... 710 .........
Aug.22 ..................... .... ........ Aug.30V ...................... .......... ..........
Aug. ..................... 825 8.0 Aug.31 ..................... .......... ..........
g. ....................... 870 8.5

SNot fed. Condition very poor; not fed.

September 1: Found dead. Autosy: Lungs congested and adhering to the pleura;
extensive inflammation of pleura; versligtly enlarged and conested; mucosa of
tomach and small intestines slightly congested; other organs normal.

Rabbit 90. Belgian, male.
Given 1 cc of 1 per cent caffein to each 100 grams through stomach tube.


Date. Weight. T t Date. ei
ment t. ment.

Grams. cC. Grams. cc.
Aug.17..................... 1,490 15.0 Aug.21....................... 1,265 12.5
Aug ...................... 1.370 14.0 Aug. 22 ..................... .......... ..........
Aug.19............. 1,35 13.5 Aug. 23....................... 1120 11.0
Aug.20........................340 13.5

I Not fed.
August 24: Found dead 9 a. Autopsy: Heart and lun appeare norm l;
bdo al viscera showed no apparent atho c change other than coccidial infe
tion of the liver and fullne of the blood vessels.







72 THE TOXICITY OF CAFFEIN

Rabbit 392. Maltese, female.
Given 1 cc of 1 per cent caffein to each 100 grams through stomach


Date. Weight. ment. Date. Weight.
me________t.ment

Grams. e Gra m. ec.
Aug. 17...................... 1 265 12.5 Aug. 26....................... 1,140 11.5
Aug. 18.................... 1,275 12.5 Aug. 27...................... 1,140 11.
Aug. 19...... ..... ........... 1,240 12.5 Aug. 281...................... .......... ........
Aug. 20..................... 1,220 12.0 Aug. 29 ...................... 1,115 11.0
Aug. 21 ....................... 1,245 12.5 Aug. 30 ....................... 1,080 11.0
Aug. 22 .............................. ........... Aug. 31 ..................... 1,020 10.0
Aug. 23...................... 1,180 12.0 Sept. 1...................... 95 10.0
Aug. 24 .............. ........ 1,190 12.0 Sept. 2...................... 930 9.0
Aug. 25...................... 1,155 11.5

1 Not fed.

Died at 3 p. m. September 2. Autopsy: The stomach and small intestines showed
numerous small hemorrhagic spots; a thick coating of mucus surrounded the con-
tents of the stomach; the other organs were apparently normal.
Rabbit 403. Black.
Given 1 cc of 1 per cent caffein for each 100 grams.

Treat- Treat-
Date. Weight. reat. Date. Weight. et
ment. mert.

Grams. cc. Grams. e.
Aug. 20..................... 1,640 16.5 Aug, 26....................... 1.390 14.0
Aug. 21..................... 1,640 16.5 Aug. 27...................... 1,330 13.5
Aug. 221 ................. ..... Aug. 28 1 ................... .......... ..........
Aug. 23..................... 1,490 15.0 Aug. 29...................... 1,130 11.
Aug. 24...................... 1,515 15.0 Aug. 30...................... 1 10.
Aug. 25...................... 1,475 15.0

1 Not fed.

August 31: Found dead at 3 p. m. Autopsy: Extensive gastroenteitis; liver
enlarged and congested; spleen slightly congested; peritoneum thickened and
congested; other organs normal.
Rabbit 384. Black, female.
Given 1 cc of 1 per cent caffein for each 100 grams through stomach tube.


Date. Weight. Treat- Date. eigt. Treat-
ment. ment.

Grams. cc. Grams. cc.
Aug. 16..................... 4,195 12.0 Aug. 25.................. ..... 90 10.0
Aug. 17....................... 1, 205 12.0 Aug. 26....................... 9.5
Aug. 18 ......................... 1,140 11.5 Aug. 27....................... 955 9.5
A ug. 19....................... ........ .... 1,180 12.0 Aug. 28 ..................... .......... .........
Aug. 20....................... 1,145 11.5 Aug. 29..................... .. 870 9.0
Aug. 21....................... 1145 11.5 Aug. 30( 2.............. ...... W 8.5
Aug. 221 ............. ....... .......... .......... Aug. 31................... ... 810 8.0
Aug. 2 .."..................... 1.. 5 10.0 S pt. 1....................... 740 7.5
Aug. 24............... .... .. 1, 10.5

SNot fed. : Por condition, mucus from rectum.

September 2: Found dead at 9 a. m. Autopsy: The mucosa of stomach showed
numerous hemorrhagic spots; the first portion of the smal intestines was slightly
congested; te other orga were apparenly normal in appeer e.







CHIINIC INTOXICATION-RABBITS. 73

Rabbit 8. Belgia, female.
Given 1 cc of 1 per cent cffein for each 100 grams through stomach tube.


Date. Weight. Treat- Date. Weight. Treat-
ment, ment.

Grams. cc. Gramt cc.
Aug. 16 ...................... 995 10.0 Aug. 22 1............................ ..........
Aug.17................... 1,005 10.0 Aug. 23......-........... 875 9.0
Au 8............ ......... 990 10.0 Aug. 24....................... 855 8.5
Aug19 .............. ... 895 9.0 Aug. 25...................... 850 8.5
....................... 945 9. Aug.26....................... 785 8.0
............ ......... 965 9.5 Aug.27....... ... ......... 710 7.0

I Not fed.

Augut 28: Found dead at 9 a. m. Autopsy: Lungs, heart, and spleen apparently
normal; liver infected with coccidia; stomach apparently normal; walls of small
intestines injected; colon marked congestion and hemorrhagic; kidneys hemorrhagic.

Rabbit 887. Belgian male.
Given 1 cc of 1 per cent caffein for each 100 rams through stomach tube.


Date. Weight. at Dat. Weight. Trt-
ment. ment.

Grams. c. Grams. cc.
g.17 ...................... 1, 20 12.5 Aug. 26.............. ... ....... 1, 15 12.0
Aug.18 ...................... 1,340 13.0 Aug.27.................... 1,255 12.5
Aug.19 .............. 1,335 13.0 Aug. 281 .............. ................ ........
Aug.20......... ......... 1,300 13.0 Aug. 29.................... 1, 115 11.0
Aug.21...................... 1,325 13.0 Aug.30..................... 1,135 11.5
Aug 1 ..................... .......... .......... Aug.31....... ............... 1,175 12.0
Aug.23...................... 1,205 12.0 Sept. 1 ....................... 1,00 10.5
Aug. 24..................... 1,200 12.0 Sept. 2....................... 900 9.0
Aug 2 ...................... 1,2 12.5

I Not fed.

September 3, found dead. Autopsy: Stomach and mall intestines showed num-
rous hemorrhagic pots; thick coating of mucus surrounded the contnts of the stom-
; bladder wa greatly distended with urine; the other organs were apparently
normal.
Rabbit 388. Belgian male.
Given 1 cc of I per cent caffein for each 100 rams, through stomach tube.


Date. Weight. Treat Date. Weight. Trat-
ment. menit.

Gra m. ee. Gra s. cc.
Aug.17....................... 1 10.0 Aug. 23 ..................... .. 1. . 10.0
Aug.1 ... ............... 1,115 11.0 Aug.24. ...... 1.0
Aug. 9 ............ ......... 11.5 Aug. .. ..................... 900 .
A ug.20.. ................... 1.130 11. Aug. 2 ....................... 875 9.0
Aug ........... 1,12 11.0 Au ...... ........ ...... 5 9.0
Aug. 221................. ... .......... .......... A ug. ...................... ......... ..........

Not fed.

August 29, found dead 9 a.m. Autopsy: Heart and lun normal; liver and kid(eys
engr ; sto ach normal intestines showed a catrrhal inflammation, though not
evere pleen normal;.wal of colon somewhat inected.







74 THE TOXICITY OF CAFFEI.

Rabbit 391. Belgian.
Given 1 cc of 1 per cent cafein to each 100 grams through stoma


Date. Weight. Treat- Date. Weight. T
ment. ment.

Grams. CC. Grams. .
Aug. 17....................... 940 9.5 Aug. 24 ................ ..... 805 8.0
Aug. 18....................... 950 9.5 Aug.25........................ 8 8.0
Aug. 19..................... 955 9.5 Aug.26....................... 765 7.
Aug. 20....................... 935 9.5 Aug. 272 ................... 690 7.0
Aug. 21 .................... 945 9.5 Aug. 281 ............................. ..........
Aug. 22 ........................................ g. 29..................... 565 5.5
Aug. 23..................... 835 8.5

1 Not fed. 2 Poor condition.

August 30, found dead 9 a. m. Autopsy: Heart injected; lungs normal; veraffected
slightly with coccidiidea; stomach normal in appearance; small intestines normal,
but colon considerably inflamed; kidneys slightly engorged; oter organs normal.
Rabbit 402. Black female.
Given 1 cc of 1 per cent caffein to each 100 grams.

Treat- Treat-
Date. Weight. ment. Date. Weight.

Grams. cc. Grams. .
Aug.20....................... 2,030 20.0 Aug.27.................... 1,765 17.5
Aug. 21...................... 1,950 19.5 Aug. 28. ....................
Aug. 22 1 ........................................ Aug.29....................... 1,630 16.5
Aug. 23................. .... 1,955 19.5 Aug.30..................... 1,540 15.5
Aug. 24...................... 1,905 19.0 Aug.31 .................... 1,510 15.0
Aug. 25....................... 1,890 19.0 Sept. 1..................... 1,425 14.0
Aug.26.................... 1,780 18.0

SNot fed.

September 2, found dead 9 a. m. Autopsy: The lungs were badly congested, the
posterior lobe of the right lung showing hepatization; the liver was considerably
enlarged and congested; the mucous membrane of the stomach and small in
was congested and showed numerous hemorrhagic spots; the kidneys showed slight
congestion; all other organs normal.

SERIES D.

The evidence brought forth in the preceding paes regarding cumulation of caffein
naturally suggests the question whether or not the body acquires a tolerance for it.
This question has already been answered in the affirmative by Gurewitch, but
owing to the method he used for the identification of caffein and the few experiments
made his results are not conclusive. The experiments of series A, B, and C might
be regarded as indicating that tolrance for caffein is not acquired by the rabbit. It
was noticed, however, that the rabbit apparently does tolerate increasingly larger
doses under certain conditions, as the following experiments show:
Rabbit 23. Belgian hare, male.
October 22: Weight, 1,520 grams; 15 cc 2 per cent caffein injected subcutaneouly
at 2 p. m.
November 1: 10.30 a. m., weight, 1,510 grams; 17 cc 2 per cent caffein injected
subcutanously (225 g per kilo), flexes observed, but no tetanus.
November 4: 10.30 a. m., weight 1,535 gras; cc 2 per cent affein injected
subcutaneously at 2.40 p. m.; 4.40 p. m., no symptoms.
November 8: Weight, 1,425 gra ; 20 cc 2 per cent caffein (285 g per kilo) injected
at 11.45 p. m.; p. m., no symptos.
November 17: Weight, 1,325 grams; 22 cce 2 per cent caffein injected at 2.55 p. m.
(329 mg per kilo), no symptoms.
November 18: Rabbit in good condition.

iil






CHRONIC INTOXICATION-DOGS. 75

t4. Belgian hare, female. Diet, carrot.
October 18: Weight, 1,935 grams; 11.20 a. m., 15 cc 2 per cent affein (155 mg per
kilo) injected.
Noveber 1: Weight, 1,780 grams; 20 cc 2 per cent caffein (224 mg per kilo) injected
bcutaneously, reflexes increased, muscle tremors present, but no other symptoms.
November 4: Weight, 1,710 grams; 21.5 cc 2 per cent caffein (252 mg per kilo)
injected.
November 8: Weight, 1,435 grams; 22.5 cc 2 per cent caffein or 314 mg per kilo
injected at 11.40 p. m.; 5 a. m., no symptoms.
November 17: Weight, 1,340 grams; .24 cc 2 per cent caffein (358 mg per kilo)
injected subcutaneously.
November 18: 9 a. m., rabbit died.
Rabbit 6. Gray male. Diet, carrots.
October 28: Weight, 1,045 grams; 10 cc 2 per cent caffein injected subeutaneously
at 1.50 p. m.; 4.30 p. m., tremors observed, but no other symptoms.
October29: Rabbit in good condition.
November 1: Weight, 950 grams; 10.55 a. m., 11 cc 2 per cent caffein injected sub-
cutaneously (231 m per kilo).
November 4: Weight, 930 grams; 2.50 p. m., 12 cc 2 per cent caffein injected sub-
cutaneously (258 m caffein per kilo).
November 6: Weight, 945 grams; 11.45 a. m., 15 cc 2 per cent caffein (313 mg per
kilo) injected subcutaneously.
November 17: Rabbit still alive; weight, 890 grams.
The results of these experiments indicate that when sufficient time is allowed
between two successive injections, susceptibility to caffein is not increased. The
bbit, on the contrary, seems to acquire a tolerance for the d for e for the fourth dose
S15 per cent larger than the minimum fatal dose of caffein. This is in all proba-
bility due to the better elimination of caffein and its products of decomposition and
Srecovery from the deleterious effects of each dose, made possible by long intervals
between injections.
The results of these experiments may be briefly summed up by stating that sub-
minimum oses of caffein given to the rabbit daily or at intervals (not Wo long) do
not produce any symptoms such as were observed in acute caffein intoxication,
namely, increased reflexes and convulsions, or increased rate of repiration, thus
showing that it is not cumulative. But evidence of undoubted summation of effect
was adduced to show that if the administration of subinimu doses of caffein
be continued daily for a period of 11 to 18 days the result is fatal. Tolerance,
however, may be acquired, although to a limited extent only, provided sufficiently
long intervals between injections are allowed to give time for repair of the injury
done by the drug and to develop a mechanism for its better decompositio and elimi-
nation. Frthermore, the evidence just given indicates that the elimination of sub-
minimum doses of caffein and its products of decomposition is probably accomplished
within 24hours or thereabouts. That the elimination of larger doses is not accm-
shed in this interval is made probable by the following expriment:
Gray rabbit 455. Female Diet, oats.
October 12: Weight 1,185 grams; 3.30 p. m., 11.5 cc 2 of per cent caffein injeced
into the lumbar musces; 3 p. m., reflexes increased
October 13: 10 a. m., rabbit weighed 1,070 rams; no sy toms of caffein poisoning
reflexes normal; 10.30 a. ., 10 c 2 per cent caffein inj into the lubar muscles;
11.30 a. m., rabbit jumped off the table, had convulsions, and died.

EXPERI NT ON DOGS.
Having gained some inforation respecting the effects of reated oses f caffein
on rabbits, it was of intert to find out how carivora reacted to the dr when sii-
laly administered. A number of d were ud for the pur Cosiderable
vaation in the mode of experientati, will appear later, was allowed.
ince the condition of athe ni al, its e, environment, or diet might be factors
fluencing toxicity, tests were made on fullrown and on youn growing dogs whose






6 THE TOXICITY OF CAFFEIN.

food was varied. The subjects of the experiment were kept under
a few days to several weeks before the administration of caein was, in
to determine whether or not any morbid condition existed, as well as to ascertain
whether the new environment had any efft on these animals. Caffein was given
chiefly by mouth, but the subcutaneous method was also employed during a por-
tion of the experimental period in some dogs. The initial dose, whh varied for
different individuals, was maintained for a variable length of time. It was the
progressively increased, in most cases until the death of the animal. With larger
doses the intervals between successive injections were also increased.
SERIES A.
SSix dogs were used in this series. Caffein was administered by mouth for periods
of six days to five weeks. It was given daily or at intervals of two, and sometimes of
three, days. In a few instances the drug was withheld for four or even for seven
days, and its administration was resumed at the end of this time. The initial dose
in these experiments varied approximately between 40 and 140 mg per kilo. The
doses were then increased gradually, and thus the maximum resistance of the subject
to caffein was tested. The diet consisted either exclusively of meat or largely of
carbohydrates with a minimum amount of meat to give flavor to the food.
Dog 11. Female.
Diet consisted of rice, 250 grams; cane sugar, 250 grams; meat, 50 grams; cracker
meal, about 100 grams. Caffein was given by mouth daily or at intervals of one day,
when the dose did not exceed 1.5 grams. Before the dose was increased to 2 grams, or
approximately 0.213 gram caffein per kilo, an interval of two days was allowed. Symp-
toms were noticed the next day. An interval of two days ws therefore allowed again
at the end of which the same dose was repeated. It will be remarked that there were
no symptoms this time, and the general condition of the dog seemed to be good. Two
grams of caffein were, therefore, given daily during the next two days without any
untoward effects; the dose was then increased to 2.5 grams. Even after this enormous
quantity no symptoms were observed except slight tremors. When this dose was
repeated 26 hours later, it proved fatal. No albumin or sugar was found in the urine,
although the dog was fed on a very liberal carbohydrate diet. The following is a
complete record of the experiment.
April 20: Urine acid, no albumin, no sugar.
April 21: Urine free from sugar.
April 22: Urine free from sugar. 1 gram caffein given in the afternoon.
April 23: 9 a. m.,-dog was very thirsty, drank a large quantity of water, urine did
not reduce Fehling's solution.
April 24: 2.30 p. m., 1 gram caffein, no sugar in urine.
April 25: 1 gra caffein administere..
April 26: Weight, 10.6 kilos, urine collected in the morning, no sugar; 4.10 p. n.,
1.5 grams caffein.
April 27: 1.5 rams caffein; 1.30 p. m., diet as before, no sugar in urine.
April 28: Weight, 10.2 kilos, no caffein, no sugar in urine.
April 30: Weight, 10.4 kilos, no sugar in urine' 4.20 p. m., 2 grams caffein.
May 1: Urine examinied, sugar absent, weiat 10 kilos, vomited, sick, tremors
observed, drank 500 cc water at one time, appetite poor.
May 2: No caffein, dranik 150 cc water.
May 3: Urine, no sugar, moderate quantity of albumen present; 12 noon, 2 ms
caffein given by mouth, weight 10.3 kilos; 2 p. m., une, ar negative, co tio
of dog (god, no symptoms of caffein intoxication.
May 4: 10 a. in., about 10 cc thick, dark-colored mucilainous urine found in col-
lecting bottle; albumin a little more than a tace, deci dedly less than on May 3,
no sugar, condoition of dog pretty good except for slight musclar tremors; 4 p. m.,
2 gras caffein by mouth (as usual .
May 5: Urine not examined, no symptoms; 4 p. m., 2 gras cffein
May 6: Urine not examined; 2.30 p. in., 2.5 gram caffein given by outh;4 p. m.,
slight treior, 110 ther syi~ptoIs.
May 7: No examination of urine, no symptoms observed; 4 p. m., 2.5 ms
caffein.
May 8: 9 a. m., found dead, urie collected since last dose of caffein was given
did not contain any suar or albumin, the amount of caffein ed to this do was 18






CHRONIC INTOXICATION-DOGS. 77

g in 18 days. Autopsy: Post-mortem examination showed marked enteritis
orrhagic pots on the mucosa; liver and kidneys congested and dark colored;
I n congested; thyroid gland was greatly enlargednd congested.

Spril 30: Weight, 6.8 kilos; the diet consised of 250 grams rice, 250 grams sugar,
100 gras cracker meal, and 100 grams of meat. On May 3 his weight was 7 kilos.
Sreceived 1 grar of caffein by mouth at 12 noon. At 2 p. m. he vomited and
tremors were observed. The next day, May 4, tremors were still present though less
nounced. Examination of the urine for sugar and albumin was negative; on
y 4, 1 caffein was given again and repeated on May 5. On this date his general
condition was not good-dog had no appetite and refused to take caffein. As the dog
lost 10 per cent of his eight he was put on a meat diet exclusively and the dose of
caffein was reduced to 0.5 gram. He became sick after the second dose, and the
miistratio of caffein was therefore discontinued. It was resumed after five days
and the caffein was administered in increasing amounts, i. e., on May 18, 0.5 gram;
y 19, 0.5; May 20, 1; May 21, 1 gram in two doses of 0.5 each, given at intervals of
hour; May 22, 1 gram. Dog became irritable, but no other symptoms were
ed The administration of caffein was omitted the next day. On the follow-
ing day when the same dose of caffein was given there was again marked irritability
ntremors. The experiment was therefore discontinued.
Dog 2. Male bulldog.
e 24: Dog weighed 13.7 kilos. Diet consisted of meat exclusively; 1 gram
caffein was given by mouth; diarrhea developed; no caffein was given for three

Jne 28: Dog weighed 13.6 kilos, 1.5 grams caffein given at 10 a. m.
June 30: 1.75 grams caffein administered.
July 2: Dog weighed 13.5 kilos; 2 grams caffein or 0.15 gram per kilo, caused well-
arked thirst, but did not produce any other symptoms.
D 0. Female:
May,12: Weight, 7.7 kilos. Fed liberal carbohydrate diet, consisting of rice, 100
sugar 100 grams; meat and cracker meal, a sufficient quantity to flavor the
May 14: Weight, 7.7 kilos. Examination of urine for albumin and sugar gave
negative results. Urine was acid to litmus.
May 17: Weight, 7.4 kilos. Three hours after it was fed the dog received 0.5
gram caffein by mouth. The test of the urine the next day for sugar was negative,
but a trace of albumin was present. It will be noticed that the doses were increased
gradually and that ymptoms were observed only after the fourth dose of 0.1 gram
per kilo. Later meat was substituted for the carbohydrate diet and the administra-
tion of caffein was stopped for four days. At the end of this period 100 mg caffein
r kilo was fed daily for five days, and the dose was then very dually increased.
iarrhea occurred twice, but no other symptoms, the second attack having lasted
a few days. The following is a complete record of the experiment:
May 19: 0.5 gram caffein 11.45 a. m.
May 20: 0.75 gra caffein 12.45 a. m.
May 21: 0.75 gram caffein 12 noon; no sugar, no albumin in urine.
May 22: 0.75 gram cffein; urine, same condition found; no syniptlns.
May 23: Weight, 7.5 kilos; no caffein.
May 24: 0.75 gra caffein; tremors very marked.
May 25: No caffein.
May 26: 0.75 gram caffein.
May 27: 0.75 gram caffein.
May 28: 0.75 gra caffein.
May 29: 1 gra caffein in two doses of 0.75 and 0.25 grai.
May 30: No caffein.
May 31: No caffein; met diet exclusively.
June 1: No caffei; mat diet exclusively.
June 2: No caffen; no sugar, no albumin in urine.
June 3: Weight, 7.6 kil; 0.75 gra caffein; no sgar in urine.
June 4: Weight, 7.3 klos; 0.75 gra affein; no uar in urine.
June 5: Weight, 7.5 kos; 0.8 grati eaffein; drank 5) cc water; ate 200 _rams meat.
June 6: eight, 7.4 kilos; 0.8 gra claffin; 00cc urine, drank 0cc water; at
200 gras meat; no symptoms.
June 7: Weight. 7.7 kilos; 0.8 gram caffein 10 a. in.; 40( cc urine, 00 c water, 200
grais meat.







78 THE TOXICITY OF CAFFEIN.

Jne 8: Weight 7.5 kilos; 0.9 gram caffein, 450 cc urine, 1 p. m.; r meat,
500 cc water.
June 9: Weight, 7.6 kilos; 0.9 gram caffein, 1 p. m.; 500 cc 200 s meat
and bone dust; diarrhea and restleness ll afternoon.
June 10: Weight, 7.6 kilos; 1 gram caffein, 500 cc water, 200 meat, 480 c
urine.
June 11: Weight, 8 kilos; 1 gram caffein, 470 cc urine, 500 cc water, 200 meat
June 12: Weight, 7.8 kilos; 1 gram caffein, 710 cc urine, 00 c water, 200 gra
meat.
June 13: 450 cc urine, 500 cowater, 00 grams meat.
June 14: Weight, 7.9 kilos; 1.2 grams caffein, 500 cc water, 300 g s meat, 490
cc urine.
June 15: Weight 7.8 kilos, 500 cc water, 300 grams meat, 550 cc urine
June 16: Weight 8.0 kilos, 1.2 gram caffein, 500 cc water, 300 grams meat, bone dust
added to check diarrhea.
June 17: 500 cc water, 300 grams meat, 450 cc urine, diarrhea continues, bone dust
added.
June 18. Weight 7.8 kilos, 1.3 gram caffein, 300 grams meat, 500 cc water, 300 cc
urine.
June 19: Dog very thirsty, drank 1 liter of water and ate 350 grams of meat; 960
cc urine passed during the past 24 hour.
June 21: Weight 7.5 kilos, 1.5 grams caffein given at 10 a. m. At 2 p. m. convul-
sions and death. This dog received a total of 21.15 grams caffein in 25 doses during
a period of 35 days, which amounts to an average of 85 mg per kilo daily.
Dog 19. Female fox terrier.
May 13: Weight 6.4 kilos. Diet consisted of rice, 100 grms; sugar, 100; and
a sufficient quantity of meat and crackei meal to give flavor to the food. Examina-
tion of the urine showed a trace of albumin but no sugar. The urine was acid to litmus.
Two days later the urine was alkaline to litmus. There was still a ll amount of
albumin but no sugar.
May 17, 0.5 gram caffein was given by mouth. Examination of the urine collected
the next day still showed the presence of albumin and the absence of reducing sub-
stances. The dog had tremors. Caffein was, therefore, not administered.
May 19: 0.5 gram caffein was given by mouth.
May 20: 0.75 gram caffein was fed at 12.45 p. m. The dog vomited during the night
and tremors were observed the next morning. The urine collected was examined
for albumin and sugar, but neither was found.
May 21: 12 noon, 0.75 gram caffein was fed. The dog weighed 6 kilos, which there-
fore represented a loss of 0.4 kilo. Grew abnormally thirsty and lost appetite, but
no other symptoms of caffein poisoning were observed.
May 22: The dog was again given 0.75 gram caffein at 12 noon. The examination
of the urine for albumin and sugar gave negative results. The dog died at 4.15 p. m.
The fatal doe for this dog was therefore 0.125 gram caffein per kilo, and the total
amount of caffein ingested in six days amounted to 3.25 grams, or 0.54 gram per day,
which makes 90 mg per kilo.
Dog 21. White female bull.
Thi dog was kept on a diet exclusively of meat, and was given water ab libitum.
From 0.5 to 0.6 gram of caffein was adminitered daily for seven days; the des were
then increased and were given at longer intervals. No symptoms of the effects of
caffein were observed until a dose of 1.5 gram was fed, when diarrhea was noticed on
the next day. In the following record the details of te experiment are given:

Date. Weight. Caffein. ate. .

Kilos. Grams. I
June 7...................... 12.5 0 June 16............. ..... .. 12.7 0.8
June 8........................ 12.5 .5 June 18......... ....... ... ... 129 1.0
June 9........................ 12. .5 June ..................... .. 2.3. 1.
June 10 ............. ......... 12.3 .6 June 24....................... 1 .3 1.
June ll....................... 12.3 .6 June 25............ ... ....... .0
June 12....................... 12.3 .6 Junme27 ...................... 13.5 1.
June 13..... ............. .. .. 12.3 June 30 ............... .. 13.5 1.7
June 14 ....................... 12.3 .8

>Diarrhea.






CHRONIC INTOXICATION-DOGS. 79

July 2: 11.30 a. m., 2.0 gram caffein fed by mouth; 1.30.p. m., tetanus, dog died.
The total a t of caffein fed to dog No. 21 out of the 25 days of the experiment was
14 grams, or an average of 578 mg per day, which ounts to about 42 to 43 per
lof dy weight.
Notwithstanding the diversity in the method of experimentation, there was a
uniformity in some of the results obtained. All the experiments of the series
wed absence of cumulative action of caffein. The experimental evidence pre-
ted indicates that moderately large doses may be given at intervals of about 24
without inducing any symptoms of nervous or any other disturbance. This is
illurated in the tests on dog 11, which were preliminary in character. In this sub-
ject 100 to 150 mg of caffein per kilo were ingested daily for several days without
showing any changes Later in the course of the experiment, after larger doses were
given, mild symptoms only, such as tremors, were observed. Additional evidence of
the absence of cumulative action of caffein was furnished by the results of the following
experiments:
Dog 23 received 142 mg of caffein per kilo on three successive days. His general
condition indicated that these amounts of caffein were toxic, but he survived. In
series of tests, made after he was allowed to rest a few days, he again failed to
show any cumulation of the drug, as he survived this time a series of tests of longer
duration than the first.
A much better illustration of the absence of cumulative action of the drug is fur-
nished by he experiments on dog No. 20. In this case 100 to 125 mg of caffein per
ki, given on 10 consecutive days, did not cause any marked effects. Diarrhea and
Sess werhe only symptoms observed. These experiments therefore show
that the elimination and decomposition of caffein are apparently effected by the body
within twenty-four hours or thereabouts.
Experiments on dog 19, however, form an exception-the third dose of 125 mg caf-
fein per kilo having proved fatal. The very low protein content of the diet of this
dog suggests itself a a possible cause of the lower resistance to caffein of this subject.
But it may be observed that the same diet was furnished to dog 20, which stood such
amounts of caffein much longer. The presence of a trace of albumin in the urine of
dog 19 is likewise inadmissible as a cause of the difference in the toxicity of caffein
in this dog, for the urine of dog 20 likewise contained a traceof albumin. The alkline
reaction of the urine, together with the fact that the first dose of only 60 mg of caffein
per kilo induced symptoms of toxicity, suggests the presence of an abnormal condition
hich in all prbability was the cause of the death of this subject under he conditions
indicated.
In a lae number of experiments on caffein performed in this laborato it has been
observed that symptoms due to caffein often disappeared when the dministration of
the same dose of the drug w continued. Thus dog 19 vomited when the aount of
caffein was increased to 125 mg per kilo. When this amount wa repeated the next
day there was no vomiting Similar observatio were made on dogs 11 and 23, als
on other dog. No. 22 developed diarrhea at first; when the administration of caffein
was resumed several days later, owever, there was no diarrhea. In other experi-
ments performed in this laboratory, symptoms of nervous irritability induced by
caffein disappeared on continued treatment.
It was interesting, to inquire whether resistance to caffein would be
increased by the continued administration of progresively larger amounts of the drug.
n does of 150 and over were fed, the intervals allowed were usually longer than
24 hour. Two and sometimes three days were peittd to elapse between two sue-
cessive doses This was done in order to allow time for recovery from possible changes
induced by laer doe of caffein, d thus prevent the summation of effect. In the
experiments considered, therefore, 11, 20, and 19, the toxicity of caffein d
not seem to be ter th in the exeriments on aute caffein ntoxication in the






80 THE TOXICITY OF CAFFEIN.

dog. It was thought, however, that the large initial doses or the quik to la
doses hen the amounts used in the beginning were small might have s thing to
do with failure to induce a marked degree of tolerance. The experiment on dog 21
was therefore carried out by giving from 40 to 60 mg per kilo for eight days, and then
increasing the dose, but tolerance could not be induced, as is shown in the protocol
to the experiment.
SERIEs B.
According to the studies of Chittenden,'1 low protein diet improves the general
metabolism of the body, fatigue is diminished, and bodily vigor, therefore, corre-
spondingly increased. The expectation is, therefore, justified that the defense of the
orgaism against deleterious substances introduced into the body is much improved
by such a diet, thus increasing its resistance to poisons. Hunt's experiment on this
subject, also quoted by Chittenden, lends support to this view. He found that mice
fed on carbohydrates chiefly, or on foods containing only a small amount of protein,
were more resistant to acetonitril. It was interesting, therefore, to inquire whether
the toxicity of caffein differs under similar conditions of diet.
A fixed diet of the same calorific value was provided for a dogs of this series, but
the protein content for three of the animals was approximately one-third of the amount
usually fed to dogs. Caffein was at first administered subcutaneouly, but all the dogs
on a low protein diet developed abscesses at the site of injection, while none of those
on high protein diet showed a local reaction. Feeding by mouth was then begun
and continued throughout the experiment in each case. The initial dose was 50 g
per kilo, which was given daily for seven to nine days. It was then increased pro-
gressively by 25 mg per kilo; 75 mg per kilo were administered for one to two days,
100 mg for two to three days, 125 mg for one to two days, 150 mg for one to two days,
and a single dose of 175 mg. It will be remarked that sometimes an interval of one
day had to be allowed during which no caffein was fed.
Dog 30. Black and tan hound, male.
The dog was under observation for about eight weeks before the experiment w
begn and had received a high protein diet. He was then given 50 mg caffein for nine
consecutive days. On the tenth day the dose was increased to 75 mg per kilo. As no
symptoms developed, this dose was increased to 100 mg per ilo, and was fed one day
apart. It was then raisedto 125 mg per kilo. For the first time since the drug was
fed, symptoms appeared they were noticed a few ours after feeding and persisted
during the next day. Although the appetite was good, no caffein was given on this
day. On the following day this dose was repeated. As the sy to were not serious,
150 mg per kilo were given daily for the next three days, until 175 mg per kilo was
reached. This dose proved fatal within six hours. Record of experiment follows:
October 9: Weight, 9 kilos, on full nitrogen diet, received daily 0.724 gram nitr
per kilo or 87 calories per kilo, received 18 grams meat per kilo, 4 grams lard per kilo,
3 gras carbohydrates per kilo, bone dust, ad libitum.
November 3: Weight, 9.10 kilos.
November 10: Weight, 9 kilos,
November 20: Weight, 9.55 kilos.
November 29: Weight, 8.70 kilos.
December 6, 7, 8, and 9: Received subcutneously 22 cc 2 per cent caffein. Cdi
tion good, site of injection noral.
December 10, 11, 12, 13, and 14: Received 0.4375 gra caffein by mouth equal to
0.050 gra per kilo, no symptoms, appetite and general conditionood.
December 1: 11.30 a. m., received 0.6563 gram caffein by ou or 0.75 gram per
kilo, no symptoms, appetite good, condition excellet.
December: 16:11 a. m., received 0.870 gram caffein by mouth, r 0.1 gram per kilo,
weight 8.70 kilos, no symptors.
December 17: No caffein given.
December 18: Received 0.870 gram caffei, or 0.1 gram per kilo, no ymptoms.
December 20: 2.45 p. m., received 1.0875 gns caffein, or 0.125 per lo; 4 p. .,
ate fd readily, eemed very uncomfortable andck.
December 21: 9 a. m., stiffnes in msles, but no other sypto, good,
no caffein given.






CHRONIC INTOXICATION-D 81

ber 22: 11 a. m., received 1.0875 grams caffein, or 0.125 gram per kilo; 3 p. m.,
depressed in spirits and sick, but no other symptoms observed.
ber 23: 11.30 a. in., received 1.305 grams caffein, or 0.150 gram caffein per
Sm., apparently quite sick, but no other symptoms, had good appetite.
De r 24: 10 a. m., received 0.175 gram caffein per kilo; 4 p. m., when about
to be fed fell over and died; no autopsy.
The total amount of caffein given dog 30 was 11.3458 grams, admin redfor a period
of teendays. The average daily amount per kilo was therefore 72 ng. The fece
offensive when the amounts of caffein were increased to 75 mg per kilo. It
Sbe observed that in this dog the appetite was uniformly good until the day of his
death. Whether or not this is che cause of his resistance to caffein will be discussed

Dog St. White, male, young.
Although he was growing rapidly this dog's weight was constant, but he looked
anemic. He received a high protein diet until December 3, when the rations were
in d by one-third. This dog was under observation from October 26 to December
Swhen the administration of caffein was begun. He then received 50 mg caffein
kilo daily for nine days consecutively without showing any effects, when the
Swas increased to 75 mg per kilo, then to 100 mg per kilo. This dose was further
d to 150 mg per kilo without causing symptoms, which was repeated the
next day. No symptoms having been observed after such amounts of caffein, 175 mg
per kilo were fed. This dose, however, proved fatal within two hours. Record of
experiment follows:
ctober 2: Weight, 6.90 kilos.
November 3: Weight, 6.90 kilos.
ovember 10: Weight, 6.90 kilos.
November 20: Weight, 6.90 kilos.
November 29: Weight, 6.55 kilos.
December 3: Put into cage, diet increased one-third.
ber 6, 7, 8, 9: Weight 6.30 kilos; 12.30 p. m., received 16 cc 2 per cent caffein
by subcutaneous injection in back, no symptoms of any kind noticed, site of injection
December 10, 14: 0.05 gram caffein per kilo.
December 15: Received 0.4725 gram caffein by mouth, no symptoms.
December 16: Received 0.655 gram caffein, 0.100 gram per kilo.
December 17: No caffein given.
December 18: Received 0.655 gr caffein daily, 0.100 gram per kilo, no symptoms.
December 20: Received 0.8188 gram caffein, 0.125 gram per kilo, no symptoms,
ecemer 21: Received 0.9825 gram caffein, 0.150 gram per kilo, somewhat uncom-
fortble, no other symptoms.
December 22: Received 0.9825 gram caffein, 0.150 gram per kilo, no symptoms
except some uneasiness.
December23: 9 a. m., no symptoms, appetite good; 11.30 a. m., received 1.146 grams
caffein, 0.1759 gram per kilo; 1.30 p. m., ded while making an effort to get out of cage,
tonic contraction of limbs observed before death.
The amount of caffein received during the entire experimental period was 9.2223
m, or an average per day aproxately of 80 mg per kilo, and therefore 10 per cent
more than dog No. 30 recved. It will be observd that the appetite in dog No. 32
Slikewise uniformly good, and that he received a very hh protein diet which was
so of a very high calorfic value.
Autop (dog 2).Stoach presented a severe inflammation of the mucosa, espe-
in the fndus and pyloric portions. The ritis was ore marked in pyloric
, and the inflammatory condition extene along the whole co of mall
testies, which presented numerous hemorrhagic areas, and a thick catarrhal exudate
on the mucosa. The lare intestine contained quite a lar-e number of parasites,
probably round worms. he liver was enlarged and the ga cyst well filled. The
sleen was also considerably engorged, kidneys appeare normal, other organs all
appeared normal.
Dog 1. Black l, male.
Snder observation one month previous t the experiments with
affein. e usual initial dose was hen administered for nine da. here were no
signs of local irritation when the drug w ven subctaneously but s pts of
toxicity were present. These disappeared, however, when the drug was administered
bymouth. The dose was therefore increased to75 mg per kilo. This, will be seen,
proved fatal within six hours. igh nitrogen diet, as No. 30.
November 3: Weight 2 kilos
1894-Bull. 148-12--






82 THE TOXICITY OF CAFFEIN.

November 10: Weight, 10.25 kilos.
November 20: Weight, 10.30 kilos.
December 1: Put in cage.
December 6, 7, 8, 9: Weight, 10.20 kilos; received 26 cc 2 per cent caffein subcu-
taneously, site of injection normal.
December 6: Very restless and excited, whined when handled as though muscles
were sore, appeared to be sick.
December 10-14: Condition good, received 0.51 gram caffein by mouth daily, no
noteworthy symptoms, appetite continues good, somewhat restless at intervals
December 15: 11.30 a. m., received 0.765 gram caffein per mouth (0.075 gram per
kilo); 2 p. m., depressed in spirit, seemed sick and uncomfortable; 4.15 p. m., when
about to feed, animal jumpe up, then fell back dead.
Autopsy (dog 31): Lungs congested; heart filled with blood and contained small
amount of blood-stained fluid in pericardial sac. Liver deeply congested, soft and
friable; gall bladder distended with bile; kidneys showed inflammation of cortex;
spleen pale, normal in size and consistency; stomach practically empty, the mucosa o
the pyloric portion exhibited severe gastritis, with thick catarrhal exudate. This
catarrhal inflammation extended through the duodenum; remaining portion of small
intestine showed mild inflammation; large intestine appply norm
The total amount of caffein received by dog 31 during 10 days was 5.395 mg, or a daily
average of 53.9 mg per kilo. This unusually low resistance to caffein which was
practically the only case in all the experiments on dogs presented in this research)
suggests the presence of some abnormal condition. The bloody exudate in the peri-
cardial cavity indicating pericarditis, which is likely to induce secondary chanes of
cardiac muscle, may be considered as a possible cause of the increased toxicity of
caffein in this case.
Dog 29. Malefox terrier, black.
This dog was kept on a low nitrogen diet for nearly five weeks before the feeding of
caffein was begun. The administration of 50 mg of caffein per kilo was then carried
on for eight days without showing any symptoms of toxicity. The usual increase of
dose was then given-75 mg per kilo-which was followed by a manifestation of
symptoms. Further increase, however, to 100 mg per kilo had no visible effect.
Nevertheless it was considered advisable to suspend the feeding of caffein for one day.
The same amounts were then repeated on two consecutive days. No symptoms having
been observed, 125 mg per kilo were given. As symptoms of toxicity and especially
loss of appetite were observed, the dog was not given any caffein the next day. Since
his appetite had now improved, the experiment with larger doses was resumed. Death
followed after the second dose of 150 mg per kilo. Protocol follows:
Weight, 9.90 kilos. One-third nitrogen diet. Receives 0.269 gram nitrogen per
kilo (88.269 calories per kilo).
November 3: Weight, 9.85 kilos.
November 10: Weight, 9.55 kilos.
November 12: Weight, 9.40 kilos.
November 29: Weight, 9.85 kilos.
December 6: Weight, 9.90 kilos; 11.35 a. m., received 25 cc 2 per cent caffein solu-
tion by subcutaneous injection in back; 4 p. m., no symptoms, appetite good.
December 7-9: Received 25 cc caffein 2 per cent solution-subcutanous injection,
no symptoms, area of injection inflamed and swollen.
December 10, 13: Site of injection showed increased inflammation, received 0.495
gram caffein (50 mg per kilo) in 30 grams meat daily without showing ay s ptoms.
December 14: 12 noon, received 0.7425 gram caffei by mouth (0.075 per kilo); 2.30
p. m., restless and uneasy.
December 15: 11.30 a. m., received 0.7425 gram caffein by mouth; 2 p. m., depresed
in spirits although continues to have good appetite.
December 16: Weight, 9.50 kilos; 3.15 p. ., received 0.9509 gram caffein by
mouth; 4.50 p. m., no symptoms.
December 17: Animal rested.
December 18: Received 0.950 gram caffein by mouth, no symptoms.
December 19: eceived 0.9509 gram caffein by mouth, no smptoms.
December 20: 2.45 p. m., received 1.1875 grans caffein (0.125 gram per kio); 4 p. m.,
restles and quite sick; ate only a little food.
December 21: 9 a. m., still uncomfortable, allowed to ret, no caffein given, grad-
ually recovered appetite.
December 22: 11 a. m., received 1.875 gram caffein; 3 p. ., seemed sick, but
showed no other symptoms, appetite fair.
December 23: 9 a. ., showed no sympto from the day before, ate food grad-
ually, seemed sick; 11.30 a. ., received 1.425 ram caffein (0.50gra perkilo); 1.30






CHRONIC INTOXICATION-DOGS. 83

p.m., looked and behaved as if very sick, no other symptoms; 3.45 p. m., in attempting
to get out of box fell over on back, had convulsions, whined, dyspnoea, died within 30
seconds.
Auto : Stomach exhibited mild inflammation; small intestine inflamed and hem-
orrhagic aea on mucosa; liver engorged and friable; spleen normal; kidneys slightly
congested; other organs appeared normal. The total amount of caffein fed to Dog 29
was 12.135 grams, which was given in 18 days. The average daily amount per kilo
was therefore 67.68 mg.
Dog 28. Male fox terrier.
Low nitrogen diet was begun about four weeks before the feeding of caffein; 50 mg
of caffein was then fed for seven consecutive days. Partial loss of appetite was
observed after the first dose. As the experiment progressed the desire for food steadily
diminished, and the feces became fetid. Symptoms of intoxication manifested them-
selves early in the experiment, and vomiting occurred after the fourth dose. The
dog was then put on a diet exclusively of meat. After an intermission of 10 days 109
mg caffein per kilo were given. Since there were no symptoms, the following day the
amount was increased to 125 mg per kilo. This dose proved fatal within 16 to 20 hours.
This dog was stout and strong, weight 12.25 kilos, received daily 0.269 gram nitrogen
per kilo (88.269 calories per kilo).
November 3: Weight, 11.75 kilos.
November 10: Weight, 11.95 kilos.
November 20: Weight, 11.20 kilos. All through this period had been kept in a cold,
poorly ventilated room, put in a warm room, with bedding and good ventilation.
November 29: Weight, 11.95 kilos.
December 1: Put in a cage; weight, 11.95 kilos.
December 6: Weight, 11.95 kilos; 11.45 a. m., received 0.050 gram caffein per kilo;
then received 30 cc 2 per cent caffein (0.6 gram) in practically one subcutaneous injec-
tion; 4.30 p. ., ate only part of food.
December 7: 10.25 a. m., received 30 cc 2 per cent caffein by subcutaneous injec-
tion (0.6 gram, or 50 mg, per kilo); 1.45 p. ., seemed sensitive to touch, no desire for
food, depressed in spirit.
December 8: 11.40 a. m., received 30 cc 2 per cent caffein by subcutaneous injec-
tion (5 mg per kilo); 1 p. m., depressed in spirit, hind legs seemed somewhat stiff,
no desire for regular food, site of injection inflamed.
December 9: 10.50 a. m., received 30 cc 2 per cent caffein by subcutaneous injec-
tion (50 mg per kilo); 2.30 p. m., had vomited, no desire for regular food.
December 10: Inflammation of site of injection, and swelling very pronounced;
2 p. m., received 0.5975 gram caffein, or 50 mg per kilo, with 30 gras of meat, refused
regular food.
December 11, 12: Received 0.5975 gram caffein by mouth, no symptoms except
refusal of regular food, fece fetid.
December 13-22: Put on meat diet exclusively, high temperature, no caffein,
weight 10 kilos, appetite good, feces fetid.
December 22: 12 m., weight 11 kilos, received 1.2 gras caffein by mouth (0.109
gram per kilo); 4 p. m., no symptoms.
December 23: 11.30 a. m., received 1.375 grams caffein (0.125 ra per kilo) had
vomited fod of the day before, but could notice no caffein or capsules in vomit; 4.30
p. m., no symptos, seemed in good spirits, appetite good, had no meat to feed with, so
was given low nitrogen feed, of which he abtout one-fourth.
December 24: 9a. m., found dea, stiff, and cold. The most striking effct of caffein
in this dog is the increased intestinal putrefaction. The feces were still fetid 10 days
after the administration of caffein wa stopped.
Autopsy, dog 28: Stomach partially filled with an undigestd fod ass; mucsa
showed severe inflamation; small intestines presented a hemorrhagic enteritis along
rver
whole extent; large intestine also exhibited mild inflanummation; liver was engorged;
spleen apeared normal; kidneys slightly congested in cortical portion; other organs
appeared normal.
Dog 4. hie and tan nalr: as put on low protein diet six wevks before experi-
mentwi caffein were begun. The initial dose of 50 m per kilo was ten admin-
itered on eight consecutive das. The only symp oms observed during this priod
of caffein administration were the of inestina putrefaction. Fetid feces were
noticed already after the fit dose of affein was inject. hen the second dose
of 75 mg of caffein was repeate, mild symptoms appeared, but none have been
observed even with inreaed moun of affein.
One-third nitrogen diet. Receiv daily 0.269 gra nitron per kilo (88.269
calories er kilo).






84 THE TOXICITY OF CAFFEIN.

October 26: Weight 11.15 kilos. Food consisted of 5 rams cracker per kilo;
meat, 3 grams per kilo; lard, 2 grams per kilo; tapioca, 10.69 gras per kilo Kept in
a cold, damp room with poor ventilation until November 20.
November 3: Weight, 11 kilos.
November 10: Weight, 10.75 kilos.
November 20: Weight, 10.55 kilos; changed to a warm room, with bedding and good
ventilation.
November 29: Weight, 10.85 kilos.
December 1: Put into a cage.
December 6: Weight, 10.90 kilos; 11.25 a. m., received 28 cc 2 per cent caffein ub-
cutaneously in side, below the shoulders, area washed with alcohl and ether,
approximately 50 mg per kilo administered, no symptoms.
December 7: 10.15 a. m., received 28 cc 2 per cent caffein injected subcutaneouly;
feces soft and very fetid; I p. m., depressed in spirit, eyes dull.
December 9: 10.45 a. m., received 25 cc 2 per cent caffein solution subcutaneously,
feces still fetid, site of injection inflamed and swollen, no other symptoms.
December 10: Inflammation of area of injection more pronounced; 2 p. m., given
0.5449 gram caffein and 30 grams of meat; 4 p. m., fed, no symptoms, feces fetid.
December 11: 12 m., given 0.5459 gram caffein and 30 grams of meat, no symptoms,
feces fetid.
December 12, 13: Given 0.5459 gram caffein daily, without noticing any symptoms.
December 14: 12 m., received 0.817 gram caffein (75 mg per kilo); 2.30 p. m., restless
and uncomfortable, no other symptoms.
December 15: 11.30 a. m., received 0.8175 gram caffein by mouth; 2 p. ., depressed
in spirit, acted as though sick, no other symptoms.
December 16: Weight, 11 kilos; 11 a. m., received 0.100 gram caffein per kilo (1.100
grams) by mouth, no symptoms.
December 17: Rested.
December 18: 2.30 p. m., received 1.100 grams caffein by mouth; 4. p. m., no
symptoms.
December 19: 12 noon, received 1.100 grams caffein by mouth; 4.15 p. m., no
symptoms.
December 20: 2.45 p. m., given 1.375 grams caffein (0.125 gram per kilo); 3.45 p. m.,
vomited-one of the capsules being found intact, the other broken open; 4 p. m.,
given regular diet, containing 1.3757 grams caffein in capsules, ate most of this during
the night, whined at intervals, coordination disturbed, appeared very sick, but
exhibited no other symptoms.
December 21: 9 a. m., found dead, stiff, and cold.
The total amount of caffein received by dog 24 was between 10.109 and 11.484 grams.
As one of the capsules vomited was intact and the other broken open, the amount was
probably about 10.75 grams. The fatal dose in this case was undoubtedly less than
185 mg per kilo-somewhere between 125 and 185 mg. Autopsy showed heart in
diastole; posterior lobe of right lung deeply congested; liver engorged; gall cyst filled
spleen appeared normal; stomach well filled with semifluid masspyoric portion o
stomach exhibited a severe inflammation of mucosa; mucosa of dodenum greatly
inflamed and showed hemorrhagic areas and catarrhal exudate; remainder of sma
intestine also exhibited mild inflammation; kidneys deeply engorged, mesentery
injected.
A comparison of the fatal doses of caffein in the experiments on high and low protein
diet does not show much difference in the resistance to caffein, since 175 mg per kilo
proved fatal to Nos. 30 and 32, while No. 29 died after receiving 150 mg per kilo, and
No. 24 received 125 to 185 mg per kilo. Moreover, No. 28, which was changed from
low to high protein diet, succumbed when given 125 mg per kilo. Observations made
during the experimental period indicate, however, geater toxicity of caffein in the
subject on low protein diet. Dog 30 showed the effects of the drug when the
dose was increaed to 125 mg of caffein per kilo, while in No. 32, 150 mg per kilo were
received without any manifestation of symptoms. og 31, which wa likewise on a
hig protein diet, is evidently an exception, and its low resistance to caffein may be
accounted for by the condition found at autopsy. In other dogs on low protein diet
symptoms of intoxication appeared early in the experiment. In Nos. 29 and 24 it
was observed as soon as the amount of caffein was increased to 75 mg per kilo. In
dog 28 the first dose of caffein 50 mg per kilo was toxic. The symptom of gatro-
intestinal disturbance were espcially marked after caffein on low rotein diet This






CHRONIC INTOXICATION-DOGS. 85

may seem to contradict the results of experiments on dogs 11 and 20, in which larger
doses of caffein failed to induce symptoms of intoxication. But it should be observed
that the diet, which consisted almost exclusively of carbohydrates, was given only
during the administration of caffein, while in the experiments of series B the sub-
jects received a low protein diet for several weeks before the administration of caffein
was begun, and it was continued through the entire caffein period. It will be re-
marked that the absence of cumulative action in the experiments of the preceding
series was also observed in dogs on high as well as on low protein diet. The appearance
of symptoms after smaller doses of caffein in the latter experiments might suggest
cumulative action, but since these symptoms disappeared on continued administration
of the substance cumulation is clearly not indicated. The gastrointestinal lesions
observed on post-mortem examination were, it will be recalled, also found in rabbits
similarly treated. The explanation suggested probably applies also in the case of
dogs.
SERIES C.
As already pointed out in the experiments on acute toxicity of caffein, young growing
dogs are probably more resistant to caffein than adults. That this may also hold true
in chronic caffein intoxication seemed indicated by the following experiments.
Dog 33. Black female puppy. Weight, 4 kilos. Had been continuously on a meat
diet.
December 22: 2.30 p. m., received 0.69 gram of caffein (0.172 gram per kilo); 3.15
p. m., no symptoms except that feces were fetid.
December 23: 11.30 a. m., received 0.79 gram of caffein (0.197 gram per kilo); 1.30
p. m., no symptoms.
December 24: 11 a. m., received 0.87 gram of caffein (0.2009 gram per kilo); 4 p. m.,
no symptoms.
It will be observed that the only effect produced in dog 33 by feeding caffein was
increased intestinal putrefaction, although 2.37 grams of caffein were given in three
days. Additional data on the effects of the age of animals on the resistance to caffein
seemed desirable. The following experiments were therefore carried out. Six puppies
of the same litter were weaned when 7 to 8 weeks old and put on a milk diet. Three
of them received this diet throughout the experimental period. Meat was substituted
in the other three a few days before the administration of caffein was begun, and was
continued until the end of the experiment. Caffein was given by mouth; the initial
dose, which was administered for several days and then gradually increased, being
160 to 200 mg for each dog, except one, which received only 100 mg per kilo for several
days and then an increased amount.







86 THE TOXICITY OF CAFFEIN.

An intermission of a few days (during which no caffein was given) was allowed
This was done on account of some studies carried on at the same time on the effect of
caffein on certain constituents of the urine.

PUP NO. 1.


Food Treatment
Date. Weight. (mi. (2 per cent Symptoms.
l. caffein).


Grams. C. c..
Apr. 21 ............ 1,450 300 10.0 No symptoms.
Apr. 22........... 1,520 300 10.0 Do.
Apr. 23............ 1,450 250 10.0 Do.
Apr. 24........ 1,375 250 10.0 Do.
Apr. 25............. 1,420 250 10.0 Do.
Apr. 26............ 1,390 250 None.
Apr. 27............ 1,400 250 None.
Apr. 28............ 1,405 250 None.
Apr. 29............ 1,420 250 None. Passed worms.
Apr.30........... 1,430 250 None. Do.
May 1.. ......... 1,450 250 10.0 No symptoms.
May 2............. 1,515 250 15.0 Do.
May 3............. 1,475 250 15.0 Do.
May 4............ 1,495 250 15.0 Do.
May 5............. 1,515 250 22.0 Seems dull and whines.
May 6............. 1,535 250 20.0 Whines.
May 7............. 1,525 250 20.0 Nosymptoms.
May8 ............. 1,530 250 20.0 Do.
May 9.............. 1,500 250 23.0 Diarrhea; passed worms; tremor and rigidity of
legs; whines.
May 10 ............ 1,490 250 None. Completely recovered from the effects of 9th.
May 11............. 1,535 250 25.0 Can not balance itself; continually vomiting.
May 12 ............ 1,460 300 None. Recovered from effects.
May 13........... 1,475 350 None. In good condition.
May 14............ 1,545 250 None.
May 15 ............ 1,550 250 None.
May 16............ 1,555 250 None.
May 17............... 1,560 250 25.0 Salivated in cage; stiffness of muscle
May 18............ 1,450 250 None. Weak and stiff; diarrhea.
May 19........... 1,500 250 None. No symptoms.
May 20....... ... 1,565 250 None.
May 21............. 1,545 250 None.
May 22............ (1) 250 None.
May 23............. 1,595 250 27.0 Tremors; gait clumsy; ncoordinaton of move-
ments.
May 24............ 1,495 250 27.0 Diarrhea; vomited; weak and stiff; found dead
9 a. m. 25th.

1 Sunday.

Autopsy: Marked pulmonary congestion; liver very pale; heart wall injected;
slight inflammation of stomach and intestines.








CHRONIC INTOXICATION-PUPPIES. 87

PUP NO. 2.


De ood Treatment
Date Weight. (milk) (2 per cent Symptoms.
caffein).


Grams. cc. cc.
Apr. 21........... 1.350 300 5.0 No symptoms.
Apr. 22......... 1,240 300 5.0 Do.
Apr.2 ............ 1,250 200 7.5 Do.
Apr. 24............. 1.205 200 7.0 Do.
Apr.25............ 1,220 200 7.0 Do.
Apr. 26............ 1,210 200 None.
Apr. 27............ 1,210 200 None.
Apr.28............ 1,205 200 one.
Apr. 29............ 1,200 200 None. Passed worms.
Apr. 30............ 1,210 200 None.
ay .......... .... 1,220 200 10.0 No symptoms.
May 2............. 1,220 200 10.0 Do.
May 3.......... .. 1.235 200 10.0 Do.
May 4.............. 1,235 200 10.0 Do.
May 5.............. 1,235 200 17.0 Whines.
May ............. 1,250 200 17.0 Do.
May 7 ............. 1,235 200 15.0 Diarrhea and worms.
May 8............. 1,250 200 15.0 Diarrhea.
May9............. 1,165 200 18.0 Little or no symptoms.
May 10............. 1,235 200 None. No symptoms.
May 11............. 1,300 200 20.0 Salivated in cage; refused to eat; draws up hind
legs.
May 12...... ....... 1200 200 None. Recovered.
May 13............. 1,215 200 None. In good condition.
May 14............ 1,280 200 None.
May 15............ 1,300 200 None.
ay 16............ 1,310 200 None.
May 17............ 1,310 200 20. 0 Salivated in cage; stiff; all symptoms.
May ............. 1,250 200 None. Weak and stifl.
May 19..... .. 1,245 200 None. No symptoms.
May20............ 1,310 200 None.
May 21............. 1,325 200 None.
May22............ 1,325 200 None.
May 23............. 1325 200 22.0 Somewhat stiff.
May 24............ 1,315 200 22.0 Restless; scratches eyes; sick.


PU P NO. 3.

Apr. 21............. 1,215 300 None.
Apr. 22............ 1,220 300 None.
Apr. 23............. 1,220 200 None.
Apr.24............. 1,200 200 None.
Apr. 2............ 1,205 200 None.
Apr. 26............ 1.195 200 None.
Apr. 27....... ..... 1. 200 200 (1)
Apr.28............. 1,215 200 one.
Apr. 29............. 1.22 200 None.
Apr. 30.........:... 1,20 2 001 None.
May ............. 1.225 200 10.0 o svymptoms.
May 2 ............. 1,230 200 10.0 fo.
May 3............ 1 25 10. 0 Coun-hs and whines.
May 4 ............. 1,245 200 10. 0 assed worms.
May 5............. 1,270 200 17.0 Eyqes appear dim and is continually sratehing
them.
May6 .............. 1,20) 200 17.0 Appears restles and dras up hind legs when
walking.
May 7.............. 1,240 20 1. 0 Eyes dim; psd worms; diarrhea.
8May 8,,,......... 1,23 2 15. C0 (ouhing continually; very rest lss.
May 9.............. 1,240 200 1. 0 12 non; slivated in ee; paed wors; diarrhea;
foaming at mouth; cn not balance himself;
rigidity and tremor of hind legs. 2.15, found


I Urine squt; ed from blsadder.

Autopsy: Severe pullnilary congestion; catarrhal gastritis; mild eniteritis with
s~Il heimorrhagic a reaas n iucosa.







88 THE TOXICITY OF CAFEIN.

PUP NO. 4.

Treatment
Date. Weight. Food. (2 per cent Symptoms.
caffein).

Grams. Milk (c). cc.
Apr.28 ........... 1,670 300 ............
Apr.29............ 1,670 300 ............
Apr.30 ............ 1,670 300 ...........
May 1............. 1,690 300 ............
May 2 ............. 1,0 300 ............
May 3....................... 300 ............
ay 4............. 1,720 300 ............
May 5............. 1,735 300 ............ q
Meat
(grams).
May 6............. 1,760 60...........
May 7............. 1,745 80............
May 8............ 1,710 180...........
May 9............. 1,750 180...........
May 10............ 1,750 180 ............
May 11 ... ..... 1,755 180 10.0 Nosymptoms.
May 12............ 1,730 180 None.
May 13............ 1,785 180 None.
May 14............ 1,835 115 10.0 Do.
May 15............ 1,820 115 10.0 Do.
May 16............ 1,835 115 10.0 Passed worms.
May 17............ 1,860 115 10.0 Feces soft and black.
May 18............ 1,855 115 15.0 Stiff; loss of appetite.
May 19............ 1,770 115 15.0 Loss of appetite.
May 20 ............ 1,755 115 15.0 Do.
May 21............ 1,780 115 17.0 Restless.
May 22 ............. ....... 115 17.0 Feces soft and black.
May 23............ 1,785 115 17.0 Loss of appetite.
May24............ 1,795 115 ............ Loss of appetite; threw up worms.
May 25............ 1,630 115 20.0 Loss of appetite; worms; cough; diarrhea.
May 26............ 1,600 115 23.0 Weak; no appetite; diarrhea; cough.
May 27............ .............................. Found dead, 9 a. m.


Autopsy.-Lung uniformly congested; liver deeply congested; heart muscle pale
with hemorrhagic areas; kidneys pale with hemorrhagic spots on surface and in
cortex; slight catarrhal inflammation of stomach and the small intestines.







CHRONIC INTOXICATION-PUPPIES. 89

PUP NO. 5.

Treatment
Date. Weight. Food. (2 per cent Symptoms.
caffein).

Grams. Milk (cc). cc.
Apr.28......... 1,745 300 ............
Apr.29........... 1,745 300 ............
S30 ............ 1,750 300 ...........
SM l............. 1,765 300 ...........
May2............. 1,765 300 ............
May 3............. .......... 300 ............
May4 ............. 1,490 300 ............
May............. 1,805 300 ............
Meat
MY 68 (grams).
May ............. 1,815 60 ............
3 ty7..Y........... 1,825 80 ............
mayS.............. 770 180 ..........
ay ............. 1,795 180 ...........
May 10............ 1,805 180 ............
May11............ 1,800 180 10.0 No symptoms.
ay12............ 1,720 180 None.
May13............ 1,815 180 None.
May14............ 1,845 115 10.0 Do.
May15............ 1,830 115 10.0 Do.
May ............ 1,815 115 10.0 Loss of weight; no other symptoms.
May17 ............ 1,830 115 15.0 Nosymptoms.
May18............ 1,835 115 15.0 Stiffness.
ay ............ 1,825 115 15.0 No symptoms.
May20............ 1,850 115 15.0 A little stiff.
ay 21............ 1,835 115 17.0 No symptoms.
ay ................... 115 17.0
May2............ 1,820 115 17.0 Do.
May24............ 1,835 115 20.0 Do.
May 25............ 1,840 115 20.0 Feces soft and black.
ay26 ............ 1,820 115 23.0
May27.......... 1,840 115 5.0 Alittlestiff.
ay ........... 1,830 115 25.0
May2.............. ..... 115 None.
...................... 115 None.
Say31............ 1,770 115 None.
J uel............. 1,765 115 25.0 Diarrhea; stiffinhindlegs.
Jue 2............. 1,750 115 27.5 Diarrhea and worms.
June 3............. 1,635 .... 27.5 Paralyzed; vomited; died at 3 p. m.







90 THE TOXICITY OF CAFFEIN.

PUP NO. 6.

Treatment
Date. Weight. Food. (2 per t S.
caffein).

Grams. Milk (cc). c.
Apr. 28...................... 300 ............
Apr29........... 1,280 300 ...........
Apr. 30............ 1,290 300 ...........
May 1............. 1,315 300 ...........
May 2............. 1,330 300 ...........
May 3............. ....... 300 ............
May 4............ 1,360 300 ............
May ............. 1,365 300 ............
Meat
(graws).
May 6............. 1,395 60 ............
May 7............. 1,365 80 ............
May 8............. 1,340 180 ............
May 9............ 1,380 180 ..........
May 10............ 1,400 180 ............
May 11............ 1,425 180 14.5 Nosymptoms.
May 12 .......... 1,470 180 None.
May 13 ......... 1,485 180 None.
May 14............ 1,510 115 14.5 Do.
May 15............ 1,500 115 14.5 Do.
May 16 .......... 1,485 115 14.5 Passed worms.
May 17............ 1,480 115 14.5
May 18 ............ 1,485 115 19.5 Feces soft and black; lmostarrhea
May 19............ 1,495 115 19.5
May 20............ 1,500 115 19.5 Scratches her eyes and hasesher tail.
May 21............ 1,500 115 17.0
May22...................... 115 17.0
May23............ 1,470 115 17.0
May 24.......... 1,465 115 20.0
May 25 ........... 1,450 115 20.0 Feces soft and black.
May 26 ........... 1,450 115 23.0 Diarrhea and worms.
May 27.......... 1,355 115 23.0 Refused to eat all food.
May28............ 1,270 115 23.0 Threw up worms, stiff, and haskinover bothey.
May 29............ ............................ Found dead.


Highest amount of caffein given, 362 mg per kilo. No autopsy.
Examination of the results obtained in the experiments of series C hows that
young and growing dogs tolerate large amounts of caffein. In four bjects of this
series, Nos. 1, 2, 3, and 6, no effect was observed when moderately large amount
(160 to 200 mg per kilo of caffein) were fed. Symptoms were noticed oy when
these amounts of caffein were increased from 50 to 60 per cent. The othertwo dogs,
Nos. 4 and 5, of this series were less resistant, however, to caffein, as 0.16 gram of he
drug per kilo induced well-marked symptoms. Since these were fed meat, while No.
1, 2, and 3 received milk, the difference in toxicity may be due to the dt employed,
but No. 6, which likewie received a meat diet, failed to show the effects of caffein
when 200 mg per kilo were fed. On the other hand, it should be noticed that No. 1
died after receiving 360 mg per kilo, No. 2 survived a dose of 334 mg, while No. 3 died
after a dose of 322 mg per kilo of caffein. The fatal doses for Nos. 4, 5, and 6 were 287,
335, and 300 mg per kilo, respectively. Although the differences are too small to
justify any definit conclusion regarding the effect of a milk diet or of a meat diet on
the toxicity of caffein, the results neverthel sugg a able iiity
caffein is more toxic to young dogs when on an exclusively meat diet than when fed
milk. It is perfectly evident, however, that the resistance to caffein in either case
very great, almost twice that of adult subjects. As shown in series A and B, 125 to
175 mg per kilo proved fatal to all but o animals in these experiments, while
symptoms of toxicity appeared after much smaller doses. In other respects the
behavior of young dogs toward caffein was the sme as that of the adlt. In neither
case was cumulation nor tolerance observed under the conditions of these exp -
ments. The findings at autopsy were likewise similar, as gastro-enteriti was the
chief lesion observed on acr opic examination. It ight be mentioned, howev






DISCUSSION OF RESULTS. 91

in this connection, that the symptoms of caffein intoxication in young dogs often
presented marked differences from those observed in those of more advanced age.
The blance of the effects of caffein in young puppies and in rabbits was very
sk In both, the tonic with clonic convulsions were observed after a sufficient
quantity of caffein was administered. In the dogs which were fully grown a large
dose of caffein was usually followed by tonic convulsions and almost instantaneous
death.
Moderately large amounts of caffein fed daily to puppies for several days-in some
caes as long as 10 days-induced mild symptoms only. No cumulative effect was
observed in any of the experiments of series C. There seems to be tolerance of certain
uctions toward caffein, but no general tolerance of the body could be obtained in
these experiments. Caffein is apparently less toxic for adult dogs on high than on low
protein diet. In young and growing dogs caffein is somewhat less toxic when milk,
rather than meat, forms the exclusive diet. Some pathological conditions apparently
increase the toxicity of caffein also in dogs. The symptoms of caffein intoxication
observed in young dogs are in some respects different from those in full grown and older
animals, and resemble those noticed in rabbits.

DISCUSSION OF RESULTS.
It was pointed out at some length in the introduction that the
toxicity of some drugs may not be the same for all forms of life.
This observation was also made by some investigators who experi-
mented with caffein on different species of animals. Thus Maurel 55
stated that caffein is twice as toxic for the frog as for the rabbit when
aministered by mouth. Fr6hner's 28 experiments, on the other hand,
made on domestic animals, failed to show great differences in the
toxicity of caffein. According to this observer, horses seem to be
more susceptible than cattle, goats, and swine, the minimum toxic
dose being the same for all of these, while the resistance of the dog to
caffein is about midway between that of the horse and the other
animals mentioned. It may be remarked, however, that Frohner made
only 13 experiments. That these data are inadequate for the forma-
tion of any conclusions ato the toxicity of caffein is evident since
the most striking effect of caffein observed in the work herein
reported was the comparatively wide range of variation in the re-
sistance of individuals of the same species to this drug. This was
found to be the case even when the conditions of experimentation
were approxiately uniform, and wa observed whatever the mode
of administration of the drug employed. The toxicity for different
dividuals also varied in acute as well as in chronic intoxication.
It is for this reason that the number of tests employed were often
quite lare, for no conclusions of any value could be drawn without
averai the results of a sufficiently large number of experiments.
Furthermore, it is to be borne in mid that the action of a drug may
differ according to the mode of its introduction into the body and
that different spcies of animals may vary in this regard. This is
especially true of some substances when given by mouth, the range






92 THE TOXICITY OF CAFFEIN.

in toxicity for certain species of animals being much ter when
thus administered than when injected subcutaneously or intrave-
nously.
Maurel's investigations are of interest in this connection, as his
work embraces a systematic study of the toxicity of a large number
of substances in the rabbit, pigeon, and frog when given by mouth,
subcutaneously, intravenously, or when injected into the muscles.
According to this investigator the range of variation of the toxicity
of a substance is widest when given by mouth. Potassium sulpho-
cyanid, for example, is about 2.5 times as toxic for the frog as for the
rabbit when given by mouth. Quinin hydrobromid is three times as
toxic for the frog as for the pigeon, while for the rabbit it is twice as
toxic as for the pigeon. When given by hypodermic injection the
toxic dose per kilo weight is practically the same for all three species.
The difference of resistance according to the mode of administration
is even more marked for spartein sulphate. When given by mouth
the toxicity for the rabbit is six times as great as for the frog, but
when injected subcutaneously the toxic dose is about the same for
the rabbit and for the frog. The relation of the mode of adminis-
tration to toxicity is further shown in the following substances: For
the rabbit the minimum fatal dose per kilo of quinin hydrobromid is
1.5 grams administered by mouth, 0.5 gram when injected subcu-
taneously, and 0.07 gram by the intravenous path, while stychnin
sulphate is twice as toxic administered intravenously as subcuta-
neously, and six times as toxic as when administered by mouth.
The mode of introduction, however, does not always affect the
toxicity of a substance. This is made evident by the action of
strychnin on frogs in which, according to Maurel I, the toxic dose is
the same whether given by mouth or injected into the subcutaneous
tissues. This appears to hold true also for other animals as demon-
strated by the experiments of Hatcher 3 on the cat, in which he
observed that strychnin is as readily absorbed from a full stomach
as from the subcutaneous tissues. These findings are extreme
interesting, especially in view of Maurel's 5' work on the subject,
according to which he finds that a substance is much less toxic when
given by mouth than when administered by hypodermic injection
or intravenously. That this generalization does not admit, however,
of universal application is made evident by the work of various
experimenters. Claude Bernard o observed that curra is as poisonous
for the pigeon when given by mouth as when injected subcutaneously,
while Zalesky found that saandarin is more toxic for frogs when
introduced into the stomach than by injection into he lymph sacs.
Our experiments with caffein likewise show that Maurel's generliza-
tion does not always hold good, since it was found in experiments with
gray rabbits that the minimum fatal dose is but moderately greater
by mouth than by the subcutaneous path.






DISCUSSION OF RESULTS. 93

Equally interesting is the observation of the writer, that in the
guinea pig the difference in the toxicity between the subcutaneous
a traperitoneal injections is very slight, while in the cat the
to ity of caffein is the same whether given by mouth or injected
into the subcutaneous tissues, and is markedly less when injected into
the peritoneal cavity. The experiments on dogs show considerable
ariation of effective dose when given by mouth, but the interest-
g observation was made that the toxic dose by mouth may be
smaller in some cases than the average dose by subcutaneous injec-
tion. If the resistance to caffein by subcutaneous injection of the
different species of animals experimented upon in the present research
be compared, it will be noticed that the gray rabbit or Belgian hare,
which is more resistant than the other varieties employed, stands
more caffein in proportion to the weight of the body than the other

Although the minimum fatal dose was found to be somewhat larger
for the guinea pig than for the gray rabbit when caffein was injected
intraperitoneally, it was on the contrary smaller by other paths of
introduction, and approximated quite closely the minimum fatal
dose for rabbits of the other varieties. Cats as well as dogs were
found to be distinctly less resistant to caffein than the herbivora.
There are a number of factors far more important than zoological
differences hich influence the toxicity of caffein. Some of these
are age, season, and pathologic conditions. As these factors have
already been dwelt upon in their appropriate places, further discus-
sion might seem unnecessary, but owing to their importance in deter-
mining the action of a drug, emphasis is desirable. Especially is this
the case with pathological conditions in relation to toxicity. While
no positive proof of diminished resistance to caffein in pathological
conditions was obtained by subjecting the suggestion to experimental
test, it was observed in these experiments on rabbits that death
occurred in some inviduals after small doses which are usually not
even toxic. The findings at autopsy indicate the presence of patho-
logical conditions. The same was observed in some experiments on
cats and dogs. It is extremely probable, therefore, that disease
modifies the reaction of the organism to caffein as well as to other
drugs.s
That the resistance to drugs ay vary according to the age of the
subject has been maintained by a number of pharmacologits. Accord-
ing to Guinard, young dogs, rabbits, and guinea pigs are very sus-
ceptible to morpi, resembling chidren this regard. The mii-
mum fatal dose for these anials is about oethird less than for the
A case of accidental posoning reported recently by Wihur (MOnich, Med. Woch., 1911, No. 3 p.
1618) throw some dobt on the accepted ew that the septlb~lty of yong hildren to Ior
ter than t of ad s. Wichu also found t t thehe rapetl d e of coe preparations or
rily recounended for chidren in peuritic cough are not elective In this condition.






94 THE TOXICITY OF CAFFEIN.

adult. This is not true, however, for the young of other species.
Cats under 15 days of age tolerate twice the toxic dose of morphin
for the adult cat. Young beeves and goats are likewise more resistant
to this alkaloid than adults. On the other hand, according to Livon,
young guinea pigs are more sensitive to alkaloids than adults. The
toxicity of caffein, as shown in the present investigation, was found
to be less in the young than in the adult. In dogs the young subjects
are in some instances almost twice as resistant as adults. The differ-
ence was found to be less in cats and rabbits than in dogs, but it was
quite marked.
The effect of season on the toxicity of drugs has been discussed in
the section on the experiments on guinea pigs, which were more re-
sistant to caffein in the fall than in February and March. The effect
of season seems to vary with the animal, but it may also differ with the
substance employed. In Noe's 5 studies on this subject cantharidin
was found to be more toxic for the hedgehog in November than in
July. The effect of season was different for morphin, as it was
observed that the resistance of the hedgehog was greater at the end
of the summer than earlier in the season.
The relation of diet to toxicity of drugs has been studed by Hunt.'
His experiments indicate that this is an important factor in the resist-
ance to acetonitril. The studies here reported on the effect of diet
on toxicity of caffein in rabbits were confined to experiments with
oats and carrots and do not show any modification of the resistance
to caffein. The question of diet in chronic intoxication in dogs, how-
ever, suggests that in these animals diet may affect the toxicity of
caffein, although the data on this subject are far from satisfactory.
There is nevertheless sufficient evidence to suggest that a hih protein
diet for the adult dog tends to greater resistance of the animal to
caffein and similarly the growing dog tolerates larger quantities of
caffein on a milk diet than on a diet of meat.
This brings us to a consideration of the behavior of caffein in
chronic intoxication. Although in both rabbits and dogs absence of
cumulation was evident, in other respects decided differences in the
resistance to cafein were observed. While the rabbit tolerate more
than twice the single dose of caffein per kilo for the dog, the result is
quite different in repeated dosage of the drug, the rabbit succumbing
to continued administration of much smaller doses of the drug than
the dog. This is probably due to lesions of the gastro-intestinal canal
caused by caffein which occasions loss of appetite much more readily
in the rabbit than in the dog. The abundant ene reserve in the
dog makes it possible for this animal to stand inanition much longer
than the rabbit and other herbivora. The difference in the behavior
of the rabbit and dog toward caffein is interesting as showing complete
reversal of resistance in acute and chronic intoxication From the





CONCLUSIONS. 95

statement in the introduction it is evident that the size of the single
to or lethal dose of a substance is in no wise an index of the active
dgr of its toxicity. The experiments with caffein here reported
furnish additional evidence that this is true, at least for the rabbit.

GENERAL SUMMARY AND CONCLUSIONS.

The toxicity of caffein in the rabbit varies with the mode of its
administration, being least when given by mouth and greatest by
intravenous administration. The toxicity is from 15 to 20 per cent
greater by subcutaneous injections than by mouth, but is about half
of that when injected into the peritoneal cavity. No difference was
observed in the toxicity of caffein whether administered into gluteal
or into the lumbar muscles. When introduced by this route the
toxicity was found to be less by one-third than when it is injected
into the peritoneal cavity, but is about 30 per cent more toxic than
the subcutaneous injections. White or black rabbits were found to
be less resistant to caffein than gray rabbits.
The resistance of the guinea pig to caffein, as of the rabbit, is
greatest when given by mouth. The minimum fatal dose is less by
intraperitoneal injections, but greater than by subcutaneous injec-
tions, thusdiffering from the rabbit in this regard. The adult cat
is lessresistant than the guinea pig or rabbit to caffein. The mini-
mum lethal dose by mouth is the same as by subcutaneous, and is
less than by intraperitoneal, injection. The minimum fatal dose
for dogs was found to be the same by mouth as by subcutaneous in-
jection and is almost the same as for the cat. The toxicity of caffein
varies in the guinea pig according to season of the year.
Age is likewise a factor in the toxicity of caffein, young animals
being more resistant than the full-grown and older animals; this was
hown in experiments on rabbits, cats, and dogs. The symln toms of
caffein poisoning also were different in pup)ies and in full-grown dogs.
Different diets, uch as carrots and oats, did not influence the resist-
ance of rabbits and guinea pigs to cafein. Low protein diet tends
to decrease resistance to caffein in ogs. Young gowing dogs are
less resistant to caffein on a meat than on a milk diet. Caffein i
not cumulative n the rabbit or dog, even if administered for a con-
siderable length of time. Some degree of tolerance may be induced
in the rabbit under certain conditions, but not in dog under the
onditions of the experimeits made in this investiation. The possi-
bility, however, that dogs may acquire tolerance for caffein is not
ecluded. Athough the rabbit olerates a much larger single dose
of caffein than the dog, it was found, in experiments on chronic
intoxication that the rabbit is less resistant to caffein than the dog.
The toxicity of caffein is probably increased under pathological con-







96 THE TOXICITY OF CAFFEIN

ditions, since comparatively smaller doses were fatal to rabbits, cats,
and dogs, when marked lesions not due to caffein found at
autopsy. Glycosuria was observed in rabbits, guinea pig, and cats
when caffein was given in sufficient amounts.

TABLE 18.-Acute cafein intoxication: Table showing average minimum toxi a
minimum fatal doses for adult animals.

Dose per kilo (grams.)
Animl. Effect of
Animal. d^-
ose. Subuta- By mouth. Intraper- Intra- Intra-
neously. itoneally. musular. venous.

TRabbit, goxic... 0. 3-00.325 0.10 125 15 0.05
abbit, gray.................... .30 .350 .150 .20 0.10-.16

abbit, white or black.......... Toxic... ........... ............ ....................... ............
Rabbit, white or black...... Fatal .... .20 .290 ............ ........................
SToxic... 0.15- .16 .150 .200 .......................
Guineapig..................... atal.... .20- .24 0.280- .300 .240- .250 ............ ............

t... .Toxic... .12- .14 .125 .125- .150 ............ ...........
...................... atal... .15 .150 .180- .200 ........................
Dog. .................... Toxic...... .100- .120 ............ ............ ............
og ..atal.... .1 .140- .150 ............ ............ ............

NOTE.-The doses given in this table are approximate.












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O