Report of preliminary investigations on the metabolism of nitrogen and carbon in the human organism

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Title:
Report of preliminary investigations on the metabolism of nitrogen and carbon in the human organism with a respiration calorimeter of special construction
Series Title:
United States. Office of Experiment Stations. Bulletin
Physical Description:
64 p. : ill. ;
Language:
English
Creator:
Atwater, W. O ( Wilbur Olin ), 1844-1907
Publisher:
Govt. Print. Off.
Place of Publication:
Washington
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Subjects

Subjects / Keywords:
Metabolism   ( lcsh )
Respiration calorimeter   ( lcsh )
Genre:
non-fiction   ( marcgt )

Notes

Statement of Responsibility:
by W. O. Atwater and others.
General Note:
With: his Methods and results of investigations on the chemistry and economy of food. Washington, 1895.

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Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029392047
oclc - 10766807
lccn - agr09002605
Classification:
nlm - WU A887m 1895
System ID:
AA00014628:00001


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BULLETIN No. 44.


U. S. DEPARTMENT


OF AGRICULTURE.


OFFICE OF EXPERIMENT STATIONS.





REPORT


OF


PRELIMINARY INVESTIGATIONS


ON THE


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WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1897.


METABOLISM OF NITROGEN AND CARBON

IN THE HUMAN ORGANISM,


WITH


A RESPIRATION CALORIMETER OF SPECIAL CONSTRUCTION.


BY


W. 0. ATWATER, Ph. D., C. D. WOODS, B. S., and F. G. BENEDICT, Ph. D.


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U. S. DEPARTMENT OF AGRICULTURE,
OFFICE OF EXPERIMENT STATIONS,
Wlashington, .D. '., June 1.S, 1W7.
SIR: I have the honor to transmit herewith a report, of investiga-
tions on the metabolism of man, in the conduct of which a respiration
calorimeter of special construction was used. The experiments with
men herein reported were made in the winter of 1895-96, at Middle-
town, Conn., under the immediate supervision of Prof. W. O. Atwater,
special agent in charge of nutrition investigations. These experi-
ments were, however, only made possible by previous researches with
special reference to the development of the apparatus and methods of
inquiry.
This work was begun in 1892 under the direction of Professor
Atwater in connection with his duties as professor of chemistry in
Wesleyan University and director of the Storrs Agricultural Experi-
ment Station. Prof. E. B. Rosa, of Wesleyan University, was asso-
ciated with the inquiry, on the physical side, from the outset. When
investigations on the food and nutrition of man were undertaken by
this Department in the fall of 1894, experiments with the respiration
calorimeter were made a part of the general plan of work, and it was
decided to extend financial aid to these special investigations, which
were already well advanced and gave promise of successful issue.
Since that time these inquiries have been conducted by the cooperation
of this Department, the Storrs Experiment Station, and Wesleyaan
University. In this way, by the expenditure of comparatively small
sums for the promotion of this particular investigation, the Departmeunt
has been able to secure for publication the results of a large amount of
original research in a line of vital importance in connection with the
establishment of a scientific basis for the nutrition of man. The work
on the respiration calorimeter was far enough advanced by the winter
of 1895-96 to justify its use in experiments with men. After several
preliminary trials, the data from which were too incomplete to warrant
publication, but which were of great service in perfecting arrangements
for the succeeding trials, the four experiments reported in this bulletin
were made.
While all the details of these experiments are not yet perfectly satis-
factory and there is still room for further improvement of the apparatus
to be used in such intricate investigations, they nevertheless mark a
3


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LETTER


OF TRANSMITTAL.






4

decided advance over work of similar character hitherto published
and give great encouragement to continued researches in this line.
The greatest success thus far has been in the measurement of the
metabolism of nitrogen and carbon, and the present report is devoted ,
chiefly to the chemical side of the investigation, which includes these
measurements. When these experiments were made the work on the
physical side, although carried on with great skill and with highly
interesting results, had not given data sufficiently accurate in all their
details to make its publication seem advisable. The investigationsare
proceeding, changes in the apparatus have already resulted in very
satisfactory physical measurements, and it is hoped before long to pub-
lish more complete data on both the physical and chemical sides of the
work.
The general management of these investigations has devolved upon
Professor Atwater. In devising and elaborating the apparatus and in
the carrying out of that part of the investigation which relates to the
measurement of the heat given off from the body and the mechanical
work done, Dr. E. B. Rosa, professor of physics of Wesleyan Univer-
sity, has rendered invaluable service. It is expected that in later
reports Professor Rosa will appear as joint author in the discussion of
the investigations from the physical standpoint. On the chemical side,
Dr. Atwater has had the assistance of Prof. C. D. Woods and Dr.
F. i(. Benedict, joint authors of this report. The skill and ingenuity
of the university mechanician, Mr. O. S. Blakeslee, have also contrib-
uted in no small degree to the practical embodiment and successful
working of the various devices adopted for the perfecting of the appa-
ratus. Other workers whose services deserve special recognition are
A. W. Smith, O. F. Tower, A. P. Bryant, and H. M. Barr.
This report is respectfully submitted, with the recommendation that
it be published as Bulletin No. 44 of this Office.
Respectfully,
A. C. TRUE,
Director.
Hon. JAMES WILSON,
Secretary of Agriculture.















CONTENTS.



Page.
INTRODUCTION ..- .......................................- .. ................. 7
General statement......................---- .............................. 7
The experiments reported in this bulletin .......................-.....---. 10
APPARATUS ....... --...-... ........-... ......- ..................... ... ...... 11
The respiration chamber .--.....------ ........-........................... 12
Appliances for ventilation and for the measurement and analysis of the
ventilating current of air............---..--------........-......---......---. 16
Air pump ..-.....-..... ... .... .. ............... .. .. ............. 18
Tension equalizer ....................... ...............-..-......... 19
Meter for measuring air .....-.......... ........ -----..---....--- ..--- 19
Aspirators for sampling air...... ..----...... --....--..............-- ..---- 20
Apparatus for determining carbon dioxide and water in samples of air. 21
METHODS OF SAMPLING AND ANALYSIS .............................-........ 22
Analysis of food, feces, and urine--.......-----------------....---........----..------- 22
Preparation and sampling of food ....--....--............ ....--.... 22
W ater ........................ ...-. ........ ...-.... ...... ......----- 24
Fat-Ether extract --...-..-...---...... ....--........--- .....----- .- 25
Ash-................................................................. 25
Nitrogen-Protein..---........ ..----- ..--- .. ........-- ....-------.--. 25
Carbon and hydrogen ----....--..- .......--- ..---...--.....-- ..... 26
Heats of combustion-Fuel val nes.....-.....-....-..-..- -.....-....- 26
Collecting, preserving, and sampling of feces and urine.........-.... 26
Analysis of respiratory products..--.. ..-- ......----------------...........--....... 27
Carbon dioxid........ .. .. ... ..... ...... ..... ......... .......... 27
Water ............................................... ......... -----------------29
Volatile organic compounds ........................................---. 31
THE EXPERIMENTS-..............-....-...................................-- 31
The diet -......- .... ..... ...-.....-.......-.....................-.. ... 32
Daily routine ... ........ ................-- ..............--------------....---- 34
Computation of results........-- ....................-- ---...-----..---.. 35
Nitrogen balance.--.-----------.........--------......-----....-----....-........--.....-------........-..---. 35
Carbon balance ... .. .... .......... ....... .... ......... ... ......... 37
Gain and loss of protein and fat ......---- .............--......----. 38
Energy .--................................................ ... ...... 39
HEi Respiration experiment No. 1 (Digestion experiment No. 11).............. 40
Respiration experiment No. 2 (Digestion experiment No. 12)..----..----..... 45
Respiration experiment No. 3 (Digestion experiment No. 13) --...--------- 48
Respiration experiment No. 4 (Digestion experiment No. 14).............. 51
Discussion of results.....................-....-....-..-..-........--..--- 56
Ventilation and production of carbon dioxid........................ 56
Nutrients and fiu l values-..... .. .... .............. ... ............ 58
+ Conclusions-------------------------------63
Conclusions ....... .................................................. .. .. ... 63
5
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ILLUSTRATIONS.




Fil;. 1. Respiration calorimeter............- ........-......................... 11
2. Plan of respiration calorinmter room.....-................-.........-. 13
3. Elevation of respiration calorimeter room.-........-..-- .........---. 15
4. Outline sketch of respiration apparatus..... ..... ................ .... 17
6


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METABOLISM OF NITROGEN AND CARBON IN THE HUMAN
ORGANISM.


INTRODUCTION.
In order to ascertain the ways in which food is used in the body and
the kinds and amounts which are best suited to people of different
classes and under different conditions it is necessary to devise accurate
methods of determining the total income and outgo of material and
energy in the organism. The importance of such a study of the funda-
S mental principles of nutrition has been recognized for many years, and
studies of one or more of the factors of the income and outgo (espe-
cially of nitrogen) have received much attention by investigators in
this field of science. Inl experiments of this nature it is customary to
express the results as a balance, in which the outgo is subtracted from
the income, thus showing the gain or loss.
GENERAL STATEMENT.
So far as the balance of material is concerned, the income consists of
food, drink, and oxygen of inhaled air; and the outgo consists of feces,
urine, and the products of respiration and perspiration. A complete
experiment on the metabolism of material would involve determinations
of the total amount of oxygen consumed, the amounts and the elenen-
tary and proximate composition of food, feces, urine, and products of
respiration and perspiration (including marsh gas from the intestines,
and similar products). For the balance of energy, the income would
include the potential energy of the food and drink; the outgo would
include the potential energy of feces and urine, products of respiration
and perspiration, and the kinetic energy given off in heat from the
body and the mechanical energy of the external muscular work per-
formed. It is possible that other less familiar forms of energy may be
conceived, but these are all which are at present known and which
may be measured. Due account must of course be taken of the tem-
perature and specific heats of food, drink, and excretory products, and
the heat used or evolved in the condensation of the water of exhalation.
A complete metabolism experiment would involve, therefore, the
determination of the following factors of income and outgo of matter
and energy:
Factors of income.
Matter: Food, drink, oxygen of air.
Elements of food, drink, and air: N, C, H, O, S, P, CI, K, Na, Mg, Ca, Fe.
Compounds of food and drink: Water, protein compounds, fats, carbohy-
drates, and mineral matters.
S Energy: Potential energy of (organic) compounds of food and drink.
r 7




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8

Factern of outgo.
Matter: Feces, nrine, products of respiration and perspiration.
Elements of above: N, C. H, 0, 8, P, Cl, K, Na, Mg, Ca, Fe.
Compounds: Water of urine and feces; carbohydrates and mineral matte
of feces; organic and mineral compounds of urine; COI, HO, and orgmaie
compounds, etc., of products of respiration ard perspiration.
Energy: Potential energy of (organic) compounds of feces, urine, and product, of
respiration, and perspiration.
Kinetic energy given oft from the body, an heat, external muscular work,
and possibly in other forms.
The above statement is, however, incomplete in that it does not
take into account the material which the body gains or loses during
the experiment and the corresponding energy stored or transformed.
This material consists mainly of water, protein compounds, and fatal,
with smaller amounts of carbohydrates, mineral matters, and other
compounds.
Tie above factors represent the gross income and outgo. The net
income would include only the material which the body actually util-
izes from food, drink, and air; that is, it represents the incomeof nutri-
ents, water, and energy consumed minus the unassimilated portion
excreted in the feces, taking into account also the incompletely oxi-
dized matter in the urine. The net income of material is that which is
taken into the circulation, builds and repairs tissue, and yields energy.
The net income of energy is the potential energy of this material plus
the energy received with the food and drink in the form of heat.
Tire gross outgo includes the total material of the excretory products,
and tihe sum of their potential energy and the kinetic energy given off
from the body. The net outgo is made up of the excretions of the kid-
neys, lungs, and skin, and tile sum of their potential energy and the
kinetic energy given off from thie body. The material and the poten-
tial energy of the feces are not utilized, but simply rejected.'
Metabolism experiments may include the measurement of the income
and outgo of one or more of the above factors. When the balance of
nitrogen, with or without mineral matter, is determined, the only fac-
tors of outgo which enter into account are the urine (sometimes includ-
ing the perspiration) and feces, since no considerable amount of nitro-
gen or mineral matter is believed to be excreted in any other form.
When tile balance of carbon, with or without oxygen and hydrogen, is
determined, the products of respiration and perspiration must be taken
into account in addition to the urine and feces. Experiments of this
nature are commonly called "respiration experiments." The experi-
ments reported here are respiration experiments, devoted especially to
the determination of the income and outgo of nitrogen and carbon.
'The residues of digestive juices and other so-called metabolic predmeo of the
feces are, it is true, a part of the material which has been digested, absorbed, ad
metabolized, but they represent material which is neither utilized for building or
repairing organs or tiuse, nor consumed to yield energy, and which, therefore, may
here be classed with the undigested residue of the food.









Investigation regarding the metabolism of matter in animals and
S man has been very active during the last forty and especially the last
twenty years. Indeed the experimental results already obtained in
this direction are much more extensive than is commonly supposed.
A compilation' has recently been prepared by this office which it is
believed includes the greater part of the experiments with man and
the lower animals in which the balance of income and outgo of one or
more chemical elements has been determined. The number of experi-
ments in which the income and outgo of energy has been measured is,
however, extremely small.
A review of this work made it evident that research upon nutrition
had reached a point where more study of the application of the laws of
the conservation of matter and of energy in the living organism was
essential. It is not enough to know the kinds and amounts of food
consumed as they are shown by dietary studies, or thle proportions that
are digested as they are learned from digestion experiments, or the
general effects of food materials as they are brought out by ordinary
feeding trials. Experiments in which the balance of income and outgo
of nitrogen are learned by weighing and analyses of food and of the
secretions of the kidneys and intestine are extremely useful, but never-
theless inadequate. The balance of income and outgo of the body must
be determined both in terms of matter and of energy. For this pur-
pose a respiration apparatus which measured only the income and outgo
of matter would not suffice. There was need of an apparatus in which
an animal or a man may be placed for a number of hours or days and
the amounts and composition of the food and drink and inhaled air, the
amounts and composition of the excreta (solid, liquid, and gaseous), the
potential energy of the materials taken into the body and given off
from it, the quantity of heat radiated from the body, and the mechani-
cal equivalent of the muscular work performed could all be determined.
Respiration apparatus of various sorts have been devised by a num-
ber of investigators. They may, perhaps, for convenience, be divided
into three classes: (1) Those in which the subject remained in a closed
chamber and was supplied with oxygen to take the place of that with-
drawn from the air by the processes of respiration. The air in the
chamber was analyzed at the beginning and end of the experiment.
(2) Those in which the subject remained in a chamber supplied with a
current of air which was measured and analyzed as it entered and left
the chamber. (3) Those in which the subject did not remain in a
chamber, but was provided with apparatus which permitted the meas-
urement and analysis of the inspired and expired air, and the deter-
mination of the respiratory quotient. In several instances the last two
forms have been combined. Calorimeters have also been devised by
mamny 1vestigatos. These have usually been combined with respira-
tion apparatus of some form.
'U. B. Dept. Agr., Office of Experiment Stations Bul. 45.







10

An excellent summary of the methods and results of respiration
experiments up to about the year 1882, with descriptions of the apparatus
employed, has been prepared by Zuntz.1 About the same time a like
excellent account of inquiries regarding the income and outgo of heat
of the body was published by Rosenthal." Since that time numerous
forms of apparatus have been devised and a large number of experi-
ments have been carried out. Reports of these are published in the
various scientific journals and have, so far as known, not yet been
sumnilmrized.
The apparatus which was used in the present experiments differs in
its essential points from that used by other investigators. It consists
of a: respiration apparatus similar in principle to that of Pettenkofer
and Voit,' which belongs to the second class mentioned above. In
addition there are devices for the measurement of the energy liberated
by the organism.
For measuring and analyzing the incoming and outgoing air, new
methods have been devised, or the methods already in use have been
materially modified. The apparatus for measuring the outgo of energy
is entirely original. Therefore, though the apparatus resembles in
outward forml the respiration apparatus of Pettenkofer and Voit, it dif-
fers in so many essential points that it may be fairly termed a new
form, and to it the name respiration calorimeter has been applied.
In the earlier experiments referred to above the subject remained in
the apparatus for short periods, usually not more than twenty-four
hours. In the present experiments the subject remained for several
days inside the respiration chamber.

THE EXPERIMENTS REPORTED IN THIS BULLETIN.

The purpose of the present article is to give a description of the
apparatus used and of the methods which have been elaborated,
together with an account of the experiments thus far made by the
authors which bear directly upon the metabolism of matter. Four
experiments with men in which the metabolism of nitrogen and carbon
has been measured are described. The results obtained regarding the
metabolism of hydrogen and energy are to be withheld until some
changes which experience has indicated to be desirable in the appa-
ratus and methods can be made, and the results already obtained can
be verified and new ones added.
The four experiments, designated by the laboratory numbers 1, 2, 3,
and 4, were as follows:
No. 1. An experiment of fifty-four hours with a laboratory assistant
No. 2. An experiment of fifty-four hours with a laboratory assistant.
'Ilermann's Handbnch der Physiologie, vol. 4, pt. 2, pp. 86-162. *
lHaldbuch der Physiologie, vol. 4, pt. 2, pp. 299-456.
3 Pettenkofer and Voit's apparatus and a number of experiments made with it are
described in U. S. Dept. Agr., Office of Experiment Stations Bul. 21, pp. 106-112.


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11

No. 3. An experiment of five (lays with a chemist.
No. 4. An experiment of twelve days with a physicist.
Several previous experiments, which were less complete, are not
reported here.
APPARATUS.

The first requisite for metabolism experiments of the kind here
reported is of course reliable methods and apparatus for the accurate
determination of the different factors of income and outgo during a
given period. This subject received much painstaking thought and
care in the present investigation. The fact, however, should be empha-
. sized that although these experiments were carried out with much
attention to detail and accuracy, they are regarded simply as )prelim-
inary to more elaborate, comprehensive, and exact investigations with
improved apparatus.


-.. -, -- -..- r A

FIG. 1.-Respiration calorimeter.

The apparatus used in the experiments herewith reported consists
essentially of a respiration chamber in which the subject stays during
the experiment, appliances for maintaining a current of air through
the respiration chamber for ventilation, apparatus for measuring and
analyzing this ventilating current of air, ; nd appliances for measuring
the heat given off from the body (see fig. 1).
The apparatus and methods for tile measurement of the heat given
off from the body, which were devised by Prof. E. B. Rosa, are believed
to be quite novel. The experience gained in the use of these appliances





. .: .... .... .
.. .... :...
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12


has naturally suggested improvements in the details. The descriptiba
of this part of the apparatus is reserved for publication after the invest.
tigations have further progressed.
The room in which the apparatus is situated and in which the larger
part of the work of the experiment is carried on is in the basement
of the Orange Judd Hall of Natural Science and is a part of the chem-
ical laboratory of Wesleyan University. It is 35J feet long, 20 feet
wide, and 9 feet high; well ventilated; supplied with gas, water, and
electricity, and heated by steam. During the period of the experi-
ments, which was in late winter, the steam heat was insufficient for
comfort during part of the night and gas stoves were used in addition.
As the building is of sandstone, with very heavy walls, the fluctuations
of temperature within, especially in the basement, are comparatively
slow. Light is supplied by five large windows, and by gas and elee-
tricity. A 1J kilowatt motor, connected with convenient shafting, fur-
nishes the power.
Opening out of this room is a smaller one, 5 by 11J feet, fitted with
arrangements for cooking the food. It also serves as a dressing room
for the subject at the times of entering and leaving the' respiration
chain er.
THE RESPIRATION CHAMBER.

The respiration chamber is a room or box in which a man may live
comfortably during the period of an experiment. The inside dimen-
sions are: Length, 2.15 meters; width, 1.22 meters; height, 1.92 meters.
It is provided with conveniences for sitting, sleeping, eating, and
working, as well as arrangements for ventilation and for the study of
the respiratory products. The chamber consists, in fact, of three con-
centric boxes, the inner one of metal and the two outer ones of wood.
The inner box, of which the inside dimensions have just been given,
is double walled, the inner wall being of sheet copper, the outer of
sheet zinc. The two walls are 8 centimeters apart. This double-walled
box is held in shape by a wooden framework between the two metal
walls. Tihe four vertical corners are rounded, as this simplifies the
construction and makes the apparatus rather more convenient for use.
The inside volume is approximately 4.8 cubic meters (see figs. 2 and 3).
An opening in the front' end of the metal chamber, 70 centimeters
high and 49 centimeters wide, serves both the purpose of a window
and a door for entrance and exit. Considerable difficulty was experi-
enced in securing an air-tight closure for this door. After numerous
unsuccessful experiments with frames of wood and metal and with India-
rubber gaskets and other appliances, the simpler plan was adopted of
using a large pane of glass in a frame as is done in ordinary windows
In these descriptions the end in which the window is situated is called the front.
The terms right and left are applied to the sides at the right and left of a person
standmg outside at the front end and facing the window.


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A 0 -- -----------






I- AT
A. Motor. Z}
B. Table. L-J
C. Sink.
W D. Air fau4.
E. Freezr for incoming air. -
F. Galvanometer. ." -- -t---
G. Brick pier.
H. Switch board. o
I. Respiration chamber. o
J. Food aperture.
K. Glass doors.
L. Thermometers.
M. Telephones.
N. Freezer for outgoing air. 0 0 0
0. Meter.
P. Tension equalizer.
Q. Pumps.,
R. Aspirators.
8. Absorption tubes.











Fla. 2.-Plan of respiration calorimeter room.






14

and securing it with putty. The labor of putting the glass in at the
beginning and taking it out at the end of an experiment is very small,
land the plan serves the )purpose admirably.
Outside of this double-walled metal box are casings of wood. The
outer wooden walls are supplied with glass doors turning on hinges
and facing the doors in the metal box.
Thie purpose t the double metal wall of the inner chamber and of
the wooden casilngs is to falcilitate the use of the devices for measure.
ments of heat. The chief use of these latter devices is in connection
with the experiments to determine the income and outgo of energy,
which ar-e not yet complete for publication.
Numerous passages through the walls are needed for tubes, to convey
the ventilating current of air and for a current of water to carry off the
heat generated by the body of the occupant of the chamber, wires for
various electric connections, metal rods for certain connections between
the interior and exterior apparatus, and, finally, the "food tube" for
passing the food and drink into the apparatus and taking out the solid
and liquid excretory products. The tubes referred to are of various
sizes and made of either brass or copper. The "ventilating tubes"
have an internal diameter of 4 centimeters. The food aperture is of
copper and has an internal diameter of 15 centimeters. It is situated
on the left side of the apparatus, and is provided with a cap at each
end. The outer cap is attached by a screw so that it may be made air-
tight. In putting in the food and other materials the cap is taken off,
the receptacle containing the food is placed in the tube and the cap put
on again. A signal is then given to the man inside who removes the
inner cap and takes out the receptacle. The materials from within are
passed out in corresponding manner. In this way there is no danger
of ingress or egress of any considerable quantity of air.
A telephone furnishes a means of communication between the inside
and outside of the chamber; the wires of the telephone pass through
rubber stoppers inserted in a tube, which, in its turn, passes through
all of the boxes and walls and is soldered to the inner copper wall.
Other wires through the same tube provide for electrical connection
with a small bell on the outside so that the person within may call an
attendant whenever desired.
Adequate provision is made for the ventilation of the chamber and
for maintaining a uniform humidity and temperature by means of the
appliances described below (p. 16). An inconvenient rise of tempera-
tu're is prevented by a current of cold water which passes through a
system of pipes inside of the chamber. This device forms a part of
the arrangements for measuring the heat given off from the body. As
the results of such measurements are not reported in this article, it will
suffice to say that the plan followed is in fact the opposite of that used
in heating houses by hot water radiators, i. e., instead of passing hot



















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1-1






FIG. 3.-Elevation of respiration calormeter room.
A. Motor. F. Galvanometer. X. Glass doors. P. Tension eqalzr
D. Table. G. Brick pier. L. Thermometers. Q. Pumps.
C. Sink. H. Switch board. M. Telephones. R. Aspirators
D. Air fans. I. Respiration chamber. N. Freezer for outgoing air. S8. Absorptiontbs
E. Freezer for incoming air. J. Food aperture. 0 Meter.


.. .. .. .. ... ..






16

water through radiators to give off heat for warming the air, cold water
is lpssed through absorbers to remove heat from the air.
A wet and dry bulb hygrometer, capable of being read to tenths of
a degree centigrade, is hung in the rear of the chamber and observa-
tions were made by the occupant, generally at intervals of two hours,
during the Iperiod of the experiment. These observations were reported
by the telephone and show the hygrometric condition of the air inside
of the apparatus.
The furniture used in the experiments consisted of a light folding
eanvals cot bed, a folding chair, and a folding table. Such clothing and
bedding as were needed for comfort were taken in by the man at the
begillninjg of the experiment, and small articles were passed in and out
through the food tube at convenient ties. The floor was protected by
carpetinhg. The alounits of water held by the furniture and clothing,
etc., were deeretrmined as accurately as practicable by weighing at the
begin lning and end of each experiment.
The arrangements for measuring and sampling the air are described
as they were actually used in tihe experiments. They have since been
replay ed by others which will be described with accounts of experi.
ments now iin progress.

APPLIANCES FOR VENTILATION AND FOR THE MEASUREMENT AND
ANALYSIS OF TIE VENTILATING CURRENT OF AIR.
A satisfactory respiration experiment involves the maintenance of a
proper current of air, the accurate measurement of its volume, and the
determination of the respiratory products. When a living subject is
in the respiration chamber and breathes its air it is essential that the
ventilation be sufficient for his comfort, but it is important that the
amount passed through the chamber be not too large, on account of
the difficulty of accurate measurement and analysis. With a small
current the reasonably accurate measurement of the volume is easier
titan with a large one, smaller samples are needed for analysis, and the
samples can be taken and the analyses made more accurately.
It is evident that the greatest care is needed to devise such mechan-
ism and methods as will secure the maximum accuracy of measurement
and sampling of the air and of determination of the respiratory prod-
ucts. Inl the large amount of work done during the last thirty years
with various modifications of the Pettenkofer apparatus the chief diffi-
culties have been in the measurement of the air and determinations of
the water. The method generally followed has been to measure both
the total volume of air and the volume of the samples by gas meters,
and to use the samples for determining the carbon dioxid and water by
absorption and the marsh gas and other volatile organic compounds
by combustion.
The same general method has been followed in these experiments.
The air was drawn through the apparatus by means of specially devised









air pumps, and its total volume measured by a gas meter especially
constructed for the purpose. The samples of incoming and outgoing air
were drawn by means of aspirators, the carbon dioxid in the sample
was determined by absorption by soda lime, and the water by absorp-
tion by sulphuric acid.
As the air was drawn and not forced through the apparatus, and
especial pains were taken to make both the respiration chamber and
the connecting pipes as nearly air-tight as possible, it was believed
tliat the air which passed through the meter and was measured by it
represented very accurately that which had passed through the cham-
ber and received the products of respiration. It is not certain that the
chamber was absolutely air-tight, but at no place could alny current of
incoming air other than that passing through the entrance and exit
tubes be found sufficient to affect the flame of a candle. Indeed, it was
hardly expected that any considerable quantity of air could enter or
pass out in any other way even if the chamber had not been tight, since














Fl. .-Outl ino sketch uf respiration apparatus.
the tension within the chamber was very slight, the barometric pres-
sure differing from that of the outside air by only a fraction of a milli-
meter of mercury. The volume of air passing through the apparatus
varied from 50 to 75 liters per minute. The longest experiment was of
twelve days' duration, and was made with an air current of approxi-
mately 55 liters per minute.
It is desirable to have the incoming current of air as dry as possible,
;js stated above. The smaller and more uniform the amounts of water
the easier and more accurate are the analytical determinations, and,
furthermore, the amount of ventilation needed for the comfort of the
occupant of the chamber is less with little than with much moisture.
:o reduce the amount to a minimum tile air which came from out of
io:ors was dried before it entered the chamber. This drying was easily
P.Ecomplished by surrounding a portion of the pipe through which it
pipssed with a freezing mixture of salt and ice.
i. 2771-No. 44-2




-v ~w.


18

The course of the air in its passage from outside through the different
parts of the apparat us to the pumps was as follows (see fig. 4): It entered
through a window by a pipe of 7.5 centimeters internal diameter and
was drawn through a freezer (Ei) consisting of a system of 10-centimeter
copper pipes packed in ice and salt; thence it was again conveyed by the
7.5 centimeter air pipe (1)) to the smaller air pipe which passes through
the front wall of the apparatus at the right of the window (B) and about
1.2 meters from the bottom of the chamber (A). In its passage from the
freezer to the chamber it was warmed so that it entered the latter at
the desired temperature. The warming was done by a 16-candlepower
incandescent electric lamp placed inside the air pipe. In this way the
temperature of the entering current of air was easily regulated. The
air entering the chamber makes a direct downward turn through a cop-
per pipe 10 centimeters in diameter which opens into thle lower right-
hand front corner of the chamber. The outgoing air is drawn from the
upper left-hand corner of the rear end of the chamber, i. e., from a point
diagonally opposite that at which the incoming air is delivered. It is
conveyed from the latter point by a 10-centimeter copper tube along
the top of the chamber to the front end and then downward to the
copper tiube (1).) through which it passes out. In this way a favorable
distribution of the air in the chamber is obtained. The diameter of the
brass tubes lias proven ample for the uninterrupted passage of such
currents of air as have been found desirable for the experiment. On
coming out of the chamber the ventilating current of air was passed
through another freezing apparatus (E2) by which the larger part of the
moisture was collected. Thence it passed through the meter (F) by
which its volume was measured and onward to the air pump (H). Since,
however, the action of the pnmp would vary the tension, a tension
equalizer (G) was placed between the pump and the meter.
Samples of the incoming air were taken from the entrance pipe just '
as it entered the chamber. Samples of the outgoing air were likewise
taken from the exit pipes just as it; entered the meter.
The several parts of this apparatus for maintenance and measuring
the current of air may be described in more detail as follows:
AIR PUMP.
Two piston pumps were used for drawing the air through the appa-
ratus. They were so arranged that either could be used alone for a
smaller current, or the two together for a larger current. In most of
the experiments here described, however, only one pump was used.
The piston of each pump was moved in a brass cylinder by cranks at.
the end of a shaft, so that each pump made a double stroke for each
revolution of the shaft. This shaft was belted to the main shaft, which
works directly from the motor, and runs at the rate of about 300 revqlu-
tions per minute. The connections were such that the pump made in
general about 75 strokes per minute. The strokes were recorded by an




-...-. -- -- --- -- .. -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -



19

ordinary automatic register reading to 100,000. As the volume of air
per stroke was known approximately this record made a rough check
upon the measuremnents with the meter. Desirable changes in the rate
of flow of air through the pump are effected by varying the length of
the stroke, the devices for this purpose being such that the desired
changes could be made with ease and accuracy. When one of the
pumps drew 65 liters per minute each stroke represented approximately
0.7 liter.
TENSION EQUALIZER.
When the pumps were connected directly with the meter the motion
of the latter was intermittent on account of the variations in air pres-
sure with each stroke of the 1)ump. To reduce these variations of
tension to a minimum and make the pressure of the air as it passed
through the meter more uniform a device was employed to which the
name tension equalizer was given. This was placed so that the air
passed through it in going from the meter to the pump. It consists of
a cylinder about 50 centimeters high and 40 centimeters in diameter.
The sides and bottom of this are of tin plate. Over the top a piece of
rubber sheeting, such as is used by dentists, is loosely stretched and
tightly bound. Although its capacity is only between 50 and 60 liters,
yet the'action of the rubber top was such that the variation in pressure
of the meter as measured by a water column amounted to only a few
millimeters, and no irregularity could be seen in the motion of the
index on the meter.
METER FOR MEASURING AIR.
The meter' was of the kind employed by Professor Zuntz, of the
Agricultural Institute of the University of Berlin, in his respiration
experiments with horses, dogs, and other animals, and with man. Pro-
fessor Zuntz was so kind as not only to assist in getting the meter, but
also to test it in his laboratory. The apparatus has been briefly
described by Professor Zuntz,2 and only the essential features will be
noticed here.
The readings of the meter are indicated by hands revolving on a
large dial and recording to 10,000 liters. In the experiments the meter
is read for the number of thousands of liters, wlile the numbers of ten
thousands of liters were checked by the register above referred to
under the head of "Air pump" (p. 18).
The accuracy of measurements of volumes of air by a gas meter has
been a subject of much discussion and no little experimenting, and the
attention given to it in this laboratory has been not inconsiderable.
The errors involved are undoubtedly small, and with care may, it is
Believed, be reduced to a very small fraction of the total volume of air
to be measured.
SMade by S. Elster, of Berlin.
L:andw. Jahrb., 18 (1889), p. 1; also Fliigge, Hygienische Untersuchungs-
ilmaethoden, p. 531.





... ....... .... I III III
.... ... .... ",, '
20

Ill using the meter a thermometer was inserted at one side, so that
its bulb was immersed in the water within the meter and its readings
were taken as indicating the temperature of the water. This was
assumed to be also the temperature of the air an it left the water. The
a*ir was assumed to be saturated with aqueous vapor at that tempera-
ture. As the air passed through at the slow rate of from 55 to 80 liters
per minute, it was not believed that this assumption involved a very
large error. It was believed, however, that meanss could be found by
which the errors of measurement could be materially reduced. An
apparatus for the purpose has been devised and made by Mr. O. 8.
Blakeslee, and tile preliminary observations made with it are quite sat-
isfactory. It is practically a large mercury pumIp, so arranged as to
serve the double purpose of maintaining the current of air and deliver-
ing aliquot samples for analysis.
ASPIRATORSC FOlt SAMPLING AIR.

The samples of air for analysis were drawn by means of aspirators (I).
These aspirators, three in number, are cylinders of galvanized iron,
standinl IIg upright, with conical ends. The cylinders are 56 centimeters
in diameter and 46 centimeters in height, exclusive of the cones which
l'rm the ends. The cones are approximately 8 centimeters in height,
making the whole length of the cylinder, from apex to apex, about 62
centimeters. At the apex of each cone is a short neck of brass tubing.
Horizontal tubes connect the two necks with an upright glass tube on
the side of the aspirator. This serves as a gauge and shows the height
of the water. It is accurately marked at the top and bottom, and thus
permits the drawing off of a definite quantity of water and consequently
the accurate measurement of the volume. The aspirators are sustained
in a framework and set in cement to give them firm support. At the top
of each is a 3-way valve, which serves to make connections with the
tubes(K~ and K,) bring ng the samplesof air. A manometer indicates the
tension and a thermometer the temperature of the air in the aspirators.
Here again the air was assumed in the experiments to be saturated at
the temperature indicated by the thermometer. The volume of water
or air held by each of these aspirators was determined by weighing the
water which it held, and was from 150 to 163 liters. The connection
between the aspirators and the tubes, through which the main current
of air passes, was made by G-centimeter brass tubes. The. sample our-
rents of air are brought from the main air current through these small
brass tubes into the apparatus for the absorption of carbon dioxid and
water (L, and L,) and then into the aspirators, by which the samples
are drawn and the volume of each sample is measured.
The rate of flow is regulated in a very simple manner. The water
passes out from the bottom of the aspirators through a short braes
tube which is connected with a longer rubber tube. The last is provided
with a screw pinchcock and a metallic nozzle at the lower end, which


R






21

is raised or lowered at will, thus varying the head of water. In tak-
ing a sample, the aspirator is first filled to the mark indicated on the
water gauge outside. The connection is made by the 3-way cock with
the tube through which the sample of air is drawn from the main cur-
rent. The flow of water from the bottom is started with the nozzle at
the end of the rubber tube at the height of about 1 meter from the floor.
The water which first comes out is collectedd in a graduated cylinder.
The amount in one minute shows the rate of flow. If this is too fast or
too slow, it is changed by means of the pinchcock on the rubber tube.
When the proper flow is established, ordinarily about 500 or 600 cubic
centimeters per minute, it is allowed to proceed. As the water level in
the aspirator falls, the nozzle is lowered and the rate of flow is observed
at intervals, generally of about one-half hour. In this way it is easy to
make the rate rapid or slow at discretion and reasonably uniform.
APPARATUS FOR DETERMINING CARBON DIOXID AND WATER IN SAMPLES OF AII,.
The constituents of the air determined in the experiments described
beyond were carbon dioxid and aqueous vapor, although only the for-
mer is reported. The device above referred to (p. 17) for removing the
moisture from the main air current by cooling to about 170 C. leaves a
small and fairly uniform amount of moisture, and thus greatly facili-
- states the determination of the latter in the samples analyzed. Four
U-tubes are used for the analysis, two, filled with soda-lime, for the
carbon dioxid, and two, containing sulphuric acid, for the water of each
sample. For weighing they are hung by loops of platinum or aluminum
wire.
Freezing apparatus.-It was found very desirable in these experi-
ments to have the air enter the respiration chamber as dry as possible.
It was with this fact in view that the plan was first adopted for freez-
ing the air before it entered the chamber. The freezer used for this
purpose consists practically of two large U-tubes of copper. These are
connected with. each other and with the pipe through which the current
of incoming air flows. They stand upright in a wooden box which is
kept filled with a freezing mixture of salt and ice. Each of the four
uprights of the two U-tubes consists of a pipe made of (No. 16) sheet
copper, 10 centimeters in diameter and 91.4 centimeters in length.
SThese upright pipes are so connected by horizontal elbows that the
Whole forms a compact mass 1 meter in length and a little over 20 cen-
timeters square. In this way the current of air has to pass through
i early 3.65 meters of copper tubing which is covered by the freezing
mixture. To still further increase the cooling surface of metal, and
with it the rapidity of the passage of heat from the air to the freezing
mixture, a number of vanes of sheet copper are placed inside the four
lengths of copper tubing. Each vane is parallel with the axis of the
Stube and is soldered to the side so as to project 3.8 centimeters toward
..the center in a radial direction. In the horizontal elbow through which
their, after having passed through the tour tubes, returns to the mainl


.," *,,.







22


conducting pipe is an orifice in which is inserted a thermometer. This
indicated the temperature of the air as it left the freezer, under ordinary
conditions to be from about- 170 to -180 C. The wooden box which
held the freezing mixture and the freezing apparatus had at the bottom
an outlet for the brine. The ice was finely crushed, mixed with salt,
and packed closely between the freezer and the box.
When the experiment was continued for twelve days, the moisture
which gathered in the form of frost on the inside of the freezing appa-
ratus accumulated so as to retard the passage of the current. Accord-
ingly the pump was stopped in the middle of the experiment, the
freezer taken out, and hot water poured upon it so as to melt the ice
inside. It was then emptied, put back in place, and repacked in the
freezing mixture. The whole operation did not last more than twenty
minutes. The stoppage of the current of air during this time did not
cause the least discomfort to the person inside the chamber. Indeed,
lie was not aware of it until he was told.
It was found necessary to repack the space outside the freezer with
ice and salt about once in two hours under ordinary conditions. This
method of removing the excess of moisture from the air before it enters
the chamber proved so satisfactory as to lead to its adoption in quanti-
tative determinations of the moisture in the outgoing air. For this
purpose, however, a somewhat more complicated freezer is necessitated
by the fact that the water which it collects must be accurately weighed.
The detailed description of this freezer is reserved for future publi-
cation.
Objections to the use of ice and salt for freezing are the trouble of
frequent renewal, the expense for material and labor, which was not
inconsiderable, the difficulty of getting a satisfactory low temperature,
and especially the impossibility of maintaining a constant tempera-
ture. For the later experiments immersing the freezers in brine cooled
by the expansion of ammonia gas has been adopted.'

METHODS OF SAMPLING AND ANALYSIS.
ANALYSIS OF FOOD, FECES, AND URINE.
The methods of analysis used were essentially those adopted by the
Association of Official Agricultural Chemists, with such modifications
as experience and circumstances have shown to be desirable.2

PREPARATION AND SAMPLING OF FOOD.
In the preparation of the food special effort was made to secure such
mechanical condition of the materials as would facilitate the most
thorough and accurate sampling. The samples, when too moist for
'The so-called "Economical Ice Machine," made by the Atlantic Refrigerating
company of Springfield, Mass., has been found very satisfactory for this purpose.
SFor detailed descriptions of the usual methods followed, with the possible sonroe
of error involved, see U. S. Dept. Agr., Division of Chemistry Bul. 46; Office of
Experiment Stations Bils. 21, pp. 39-52, and 29, pp. 8,9.







23


grinding, were partially dried: the material in the original or partially
dried form was sampled and ground, first in an ordinary Excelsior
mill," afterwards in a Maercker-D)reefs mill, by which it is easily
reduced to a very fine powder. Some materials, containing consider-
able quanttities of fat or sugars, are not easily ground in this way.
Meats, eggs, and canned pears, for instance, were rubbed in a mortar
until they were homogeneous. The ground material was preserved for
analysis in tightly stoppered bottles. It has been found, however, that
*hen such materials are kept in bottles closed with glass, or even rub-
ber stoppers, they are apt to change in moisture content on long stand-
ing. Unless the analyses are to be made immediately, or within three
or four days at longest, it is best to seal glass-stoppered bottles with
paraffin. Even then, if the material has stood for some weeks, it will
sometimes be found desirable to repeat the determinations of moisture.
When nearly all the water is removed from tnhe materials, as is done in
the process of partial drying referred to beyond (p. 24), no indications
of decomposition, even of meats, were found for some weeks or months.
It is, however, noticeable that when tlie samples of meats containing
more or less fat are thus dried and finely ground, and are allowed to
stand in the working room of the laboratory, the fat gradually sepa-
rates and settles to the bottom of the bottle. This is an indication of
the need of careful mixing of such materials just before the weighing
of portions for analysis.
Some food materials, however, are so dry as not to require the partial
drying. Ordinary fine wheat flour is ready for analysis at once, or can
be preserved for some time in tightly closed bottles. The coarser flours
and meals, rice, and common crackers and biscuit can generally be
ground and kept for analysis without drying.
Since in some instances the treatment was somewhat detailed, the
methods used for the preparation of each kind of food for analysis may
be briefly outlined.
Beef.-A lean piece of round steak was selected and the superfluous
fat was carefully removed. The meat was then cut in long strips and
run through a meat chopper several times, thus securing fine division
and thorough mixture. After leaving the chopper it was weighed out
in balls or.cakes of 62. grains each, and placed on a plate covered with
a glass cover. When meat was cooked for a meal three of these balls
were cooked at the same time and in the same disl; two of them were
eaten, and the third served as a sample for analysis.
Bread.-Three kinds were used, white bread," made of fine wheat
flour; "brown bread," of wheat and rye flour and corn meal; and rye
bread. To insure like composition and like proportions of crust and
crumb, the loaf was cut in slices and alternate slices were taken for
eating and analysis.
Oatmeal.-One of the common commercial preparations of oatmeal
was used. A certain weight of the dry material was cooked in water.
. As there was no reason to fear loss of material the composition of the







24

oatmeal as eaten was assumed from that of the original material, ta. '
ing into account the water added in cooking.
Potatoes.-These were boiled with the skins on. After pouring off
the water the skins were removed and the potatoes put through a potatoiiiII..
masher. The portion to be eaten was weighed, a sample of like weight
being taken at the same time for analysis.
Apples.-The fresh fruit was pared and the cores removed, nothing
but the apple pulp being eaten by the subject. Samples of the pulp
were analyzed.
Canned beans, pears, and peaches.-These three materials were served
cold, and required no special preparation. Samples from the different
cans were used for analysis.
Milk crackers, sugar, and cheese.-These were served as purchased in
the market, without any special preparation. Samples of each lot were
analyzed.
Eygn.-Eggs of approximately the same weight were selected. Three
were boiled in the same dish of water, two were eaten, and one was
taken as a sample.
Bhuter.-This was a creamery butter as purchlased. No partial dry-
ing was necessary. Samples were taken at each meal, each sample
being of the same weight as the portion eaten.
M1ilk.-Aliquot portions were taken from the milk of each day.
These samples were preserved until analyzed by addition of potassium
bichromate.
As fast as samples were taken they were either immediately "partially
dried," as in the case of meat, bread, potatoes, etc., or preserved for future
analysis by some antiseptic, such as potassium bichromate, as in the case
of milk. The several samples of a given material for a given period were
joined together and resampled, so that a single analysis served for the
whole of that special lot. Thus the several samples of "white" bread
for a given number of days were united, and after the partial drying
were well mixed and a single sample representing the whole was
analyzed. This course was followed with the other materials in so far
as it was feasible without risk of inaccuracy.
WATER.
Partial dry/ing.-For this process portions of 50 grams each were
placed in shallow porcelain sauce dishes and heated in a large air bath
at the usual temperature of 960 C. or thereabouts for a period of thirty-
six hours. They were then placed on a shelf lightly covered with paper,
and thus exposed to the air in the klboratory for twenty-four hours.
At the end of this time the moisture content had become practically
constant and the samples were weighed and the loss of moisture noted.
They were then ground, placed in properly marked bottles, and set
aside for analysis.
Complete drying.-For the determination of water-free substance the
usual methods were employed. The time of drying was usually five







I 25

hours. in accordance with the official methods. This, however, did not
suffice in all cases, and longer heating was necessary. It is well
known that one of the most difficult operations in the laboratory is the
accurate determination of moisture in animal and vegetable substances,
and not a little work has been done in this laboratory with a view to
improving the accuracy of moisture determinations.'
FAT-ETIIER EXTRACT.

The sample which had been dried in hydrogen for the water determi-
nation was used for the determination of crude fat. To this end it was
extracted in the usual way with ether, which hlad been digested with
fused calcium chlorid and distilled over that substance. Continuous
extraction for sixteen hours was generally sufficient.
ASH.

For determination of ash the material was incinerated in tie follow-
ing manner: The mass was first charred in a platinum capsule and
then extracted with hot distilled water, the insoluble matter being
collected on a filter; the filter with its contents was then returned to
the platinum capsule and the whole heated until the incineration was
complete. The aqueous extract was added, and after evaporation the
whole residue was heated at low redness until the ash was white.

NITROGEN-PROTEIN.

Nitrogen was determined by the Kjeldahl method, the amount of
nitrogen thus found multiplied by 6.25 being taken as representing the
protein. As the proportion of nitrogen is the basis of the calculations
of nitrogen balance, the method of estimating protein by differences,
which is often followed in analysis of meats and other materials con-
taining little or no carbohydrates and which is doubtless often more
accurate, would not be in place here.
Experience in this laboratory with meats and other animal tissues
confirms the observations of other cheinists that there is great danger
of incomplete ammonification of the nitrogen in these substances when
treated with sulphuric acid and other reagents as ordinarily recom-
mended in the Kjeldahl process. It appears tlhat numerous albuininoid
substances resist decomposition, or at any rate the complete union of
nitrogen and hydrogen to form ammonia. Witll such substances it was
found necessary to continue the digestion for some time after the sul-
phuric-acid solution had become colorless. The clearness of the solu-
tion was by no means an indication of complete aminonificaition. The
process has frequently been found to be incomplete when the digestion
Shad been continued for an hour or even two hours after tlhe disappear-
ance of color. It is safer to continue the digestion for three or four
Hours after the solution has become decolorized.
[.... See U. S. Dept. Agr., Office of E:xpriimeut Stations ull. 21, p. 41.





: ... ... : :....... :

26

Casein.-In analysis of butter the casein was determined direedly
The butter was placed in a (ooch crucible and the fat dissolved oat
with ether. The casein and mineral matters were weighed together and
the casein burned. The loss in weight on burning was taken as repre-
senting the (asein. The danger of slight error here on account of the
presence of milk sugar is a subject which has not been investigated,

CARBON AND IIYDROGIEN.
The food materials, feces, and dried urine were burned with cuprle
oxid with the aid of a current of oxygen, in accordance with the usual
methods. The carbon dioxid was absorbed by potassium hydroxid anad
the water by concentrated sulphuric acid.'

EATS OF COMBUSTION-FUEL VALUES.

The determinations of heats of combustion of food materials, feces,
and dried residue of urine were made with the bomb calorimeter, as
described in previous publications.2 The apparatus and method
have been in use in this laboratory for the past three years, and have
been found very satisfactory.

cOLLE('TING, IPIESERVING, AND SAMPLIING OF FECES AN) URINE.

In the digestion experiments (which began before the subject entered
the respiration chamber, as explained beyond) it was necessary that
the feces of a given diet should be separated from those of the diet
immediately preceding. To effect a sharp separation the subject had a
supper of bread and milk, at which time he took six or seven large gel-
atin capsules containing lampblack.: The following morning the diet
decided upon for the digestion experiment was begun and strictly
adhered to throughout the wlole experiment. Tihe sampling of food
for analysis was also begun at this first meal. On the second or third
day tile milk feces, having a characteristic consistency and colored with
lainlpbick, generally appeared. When there was no indication of
diarrhea, the separation of the residues from the two different kinds of
fi1od may be considered reasonably ,accurate inasmuch as the portion
from the meal of bread and milk is easily distinguished from that of
ihe succeeding meal. All the feces following that of the bread and
milk were saved. At the end of the experiment a supper of bread and
milk with lampblack was again taken, and all the feces up to the
point where the milk residue appeared were considered as belonging
to thie iui ligested residues of the diet under study. At first the feces
of each day during the experiment were separated, weighed, and in
I For observations upon the Mources of error in the ordinary methods of analysis of
animal and vegetable products, see U. S. Dept. Agr., Office of Experiment Stations
Bul. 21, pp. 38-52.
'IT S. Dept. Agr., Olnice of Experiment stations Bidl. 21. pp. 123-126; Connecticut
Storm Sta. 1pt. 189.1, pp. 135-157.
:'Later experience hItS shown that mo much lampblack is unnecessary. A


_I I _







27


some cases separately analyzed also. This, however, proved unnec-
essary, as it was found that the composition with a given diet remained
very nearly the same from day to day.
The urine is obviously a very important factor as regards the metabo-
lism of nitrogen. Consequently its collection and preservation for
analysis require especial attention. Unfortunately it was possible to
give only limited attention to the subject during these experiments. It
is believed that a more thorough investigation of thee character and
constituents of urine in respiration experiments will prove of no little
physiological importance.
In these experiments the bladder was emptied every morning at 6
o'clock. All the urine voided between that hour and the next morning
at the same hour was taken as the urine for that day. Each day's
urine was carefully weighed, thymol being added as a preserving agent.
The total nitrogen in the urine was determined in the fresh substance
by the Kjeldahl method.
For the determination of carbon and hydrogen the urine was dried
in a partial vacuum over sulphuric acid. It was found by repeated
tests that drying urine by heat involves considerable loss of nitrogen.
The importance of avoiding this loss led to investigations which showed
that fresh urine could be dried in a vacuum over sulphuric acid with-
out material loss of nitrogen. Accordingly it was assumed that there
would also be extremely little loss of carbon and hydrogen, and the
substance thus dried was taken for the determinations of these ele-
ments. The same method was followed, though generally with a some-
what longer period of drying, to determine the amount of water-free
substance. The percentage of water in this partially dried il. racfo"
nrine was taken into account in calculating the percentage of carbon
as determined by combustion with cupric oxid.

ANALYSIS OF RESPIRATORY PRODUCTS.

In experiments of the class to which those here reported belong the
respiratory products commonly determined are carbon dioxide, water,
and volatile organic compounds.

CARBON DIOXIDE.
The determination of carbon dioxide is most essential, and is, of course,
always attempted. The experience of a number of experimenters dur-
ing the past twenty-five years implies tlat the difficulties in the way of
fairly accurate results are not insuperable. The carbon dioxide given
off in respiration is quickly diffused through the air and readily con-
veyed away by the ventilating current, so that the accurate measure-
ment of that current and determination of the percentage of carbon
dioxid suffices for the ordinary purposes of experiment.
For the absorption of carbon d(ioxid soda-lime has, in our experience,
proved the most satisfactory reagent. It must, however, have the









proper proportions of Roda, lime, and water to fit it for the purpose
It may be made as follows: One kilogram of commercial caustic soda
is treated witl 000 cubic centimeters of water, forming a very strong
solution, or rather a pasty mass. To this a kilogram of quicklime is
added. The latter is slaked by the water of the soda solution. The
mixture is rapidly stirred. No heating is necessary. If there are any
lumps, they are broken into small pieces, and the soda-lime thus made
is immediately put into large bottles or fruit jars and tightly sealed.
The presence of a certain amount of moisture in the soda-lime is
essential to the complete absorption of the carbon dioxid. As the soda-
lime is converted into the carbonites of sodium and calcium the mass
whitens, and the advancement of this change in color from one end of
tihe column of soda-lime to the other is apparent as the absorption of
carbon dioxide proceeds. This affords a very good check on the effi-
ciency of the tube. In the preliminary tests of the method, as in the
actual determinations, two tubes were used in series, and after each
determinant ion the second tube was moved toward the incoming uenrrent,
so that it became t.lhe first tube, and a fresh one was inserted to serve
as second tube. Numerous experiments were made with varying quan-
tities of carbon dioxide in the air and with varying rates of flow to see
if the system would thoroughly remove all carbon dioxid. A check
tube containing glass beads drenched with barium-liydroxid solution
failed to indicate the slightest trace of carbon dioxide, with 150 litersof
aspirated air, containing 3.5 grains of carbon dioxid, and running at
the rate of 500 cubic centimeters per minute.
Thle value of the soda-lime as an absorbent for carbon dioxid was
further demonstrated by passing a current of air previously freed from
carbon dioxide through a flask in which a known quantity of carbon
dioxid was generated from pure sodium carbonate or calcite. As the
air with this carbon dioxide came from the flask it was passed over sal- .
phuric acid to absorb the water and then through two tubes containing
soda-lime, then through a tube with sulphuric acid to catch the water
setr free from the soda-lhme, and finally through a tube containing
bariumn-hlydroxid solution to detect any traces of carbon dioxid which
might fail to be absorbed by the soda-lime.
After considerable experience in testing the methods by control
experiments of various kinds an arrangement of absorption tubes for
water and carbon dioxide was settled upon, and has skice proved very
satisfactory. The order is: First, a tube filled with pumice stone satu-
rated with sulphuric acid for thie removal of water; then two tubes
filled with soda lime for the absorption of the carbon dioxid;. and
finally a sulphuric-acid tube to absorb the water removed from the
soda-lime by the current of air and set free in the formation of carbon-
ates by the action of the carbon dioxide upon the hydroxids.
It was found important, however, to pass a current of dry air through :
the sul phuric-acid tubes for three or four hours before they were used j







29


Sfor the determinations, since it was observed that the freshly filled
tubes lost weight when dry air was first drawn through tlieiii, ti loss
sometimes amounting to 20 milligrams. A plausible explanation of
This loss would be found in thie assumption that incompletely oxidized
compounds of sulphur or nitrogen which were either originally present
in the acid or were formed by its action on the organic matter inl the
pumice stone were removed by the air when first passed through tihe
tube. As the method for avoiding the error proved situmple and effective,
we have not taken the time to inquire more fully into the cause.
The determination of carbon dioxide by the above method is quite
satisfactory, as was shown by numerous control experiments. In one
experiment, for instance, which was fairly representative of all, 1.(69)2
grams of carbon dioxide were delivered into the air current and 1.6718
Grams were removed in the soda-lime.
The weighing were all made with a counterpoise. To insure equal
moisture condensation on the tubes and counterpoise, the latter was
kept in the tray with the U-tubes, and hence subjected to like conditions
of temperature and moisture.
WATER.

The accurate determination of water has been found less easy. The
difficulty appears to rest not so much in the determination of moisture
in the current of air as in the getting of all the moisture into the cur-
rent. It is believed that one chief trouble here may be tile adhering of
moisture to the surfaces of the walls and other interior parts of the
apparatus and its absorption by the clothing of. the subject and the
furniture in the respiration chamber. It is evident that for reliable
.results two things are requisite. One is an accurate and convenient
method for the determination of water in a current of air, the other a
means for either making sure that all the water to be determined is
contained in the air current or that the amount not in that current
shall be determined in some other way. The water to be determined
is the whole given off from the body of the subject in the respiration
chamber, less the amount removed in feces and urine. Practically this
means the water exhaled through the lungs and skin. For our present
purpose it may be designated as water of exhalation and taken as
including the water of respiration from the lungs and that of perspira-
tion from the skin. Since the various difficulties encountered in the
accurate determination of water had not been satisfactorily overcome
when these experiments were made, the results of such determinations
are not reported in this article.
The test of the reliability of the methods for the determination of
the products given off from the body of the person in the respiration
chamber must be found in check experiments in which known quanti-
I:ies of the same products will be given off in the chamber and deter-
Imined in the air current by the methods used for the actual experiments.







30

Numerous check experiments of this kind preceded the experiments
with imen reported beyond. The results indicated that the deterui
tions of carbon dioxide were reasonably accurate. The same was also
true of tihe water as far as concerned the amounts actually contained
inl the incoming and outgoing currents of air. It was not certain, how-
ever, that the moisture which was condensed upon the interior surface
of the apparatus (especially upon that part of the apparatus within
thle chamber through which the cold water passed to carry away the
heat and to which tlhe term heat absorbers has been applied) was the
sample at the beginning as at the end of tile experiment. The assump-
tioni that tIhe methods for tlIe determinat ion of carl oni dioxide and water
in the currents of air and for the determinations of the amounts of
carbonic acid inl tihe apparatus were reasonably accurate was further
substantiated by check experiments whicl followed the present experi-
Inents within men.
The most satisfactory of these were made by burning ethyl alcohol
inside tihe chamber. Tile determinations of carbonic acid differed by
less than one-hallf of I per cAet from the theoretical. In other words,
for every 10(0 grais (of carbon in the alcohol the measurements gave
fronm 9).! to 100.4 grams. So falr aIs concerns the determination of car-
bonic acid given oil' inside the apparatus, the only difference between
these check experiments with alcohol and the experiments with men
reported beyond was in the measurement of the air current, which
could hardly have n made any very importantt difference in the results.
It is believed, therefore, that the determination of carbon dioxid given
off by tihe men iin the experiments beyond can not be very far from
correct.'
'Before the check experiments were made, arrangements were perfected by which
the absorption apparatus could he weighed by the man inside the chamber, so that
the changes in the amounts of water condensed upon the surface of the absorbers
could leo learned. The measurements of the volume of the air were made by the
improved apparatus referred to above. (See p. 20.)
In the check experiments with alcohol the determinations of water could not be
niade with tlhe same accuracy as in the experiments with men, since in the latter case
thu absorption apparatus could be weighed by the person inside the chamber. It is
however, possible so to regulate the combustion of the alcohol, and hence the pro-
duiction of carboon dioxide, water, and heat, that the amounts produced duringagiven
period at the beginning of an experiment shall lie very nearly the same as during a
like period at the end. I'ndcr these circumstances the amounts of water condensed
on the absorbers at the ends of the two periods will be approximately the same.
The control of the amount of water condensed upon the absorbers is facilitated by
tle ease with which both the temperature of the interior of the apparatus and the
proportion of water in the incoming air current may be regulated.
In the check experiments made by burning alcohol in the chamber, pains were
taken to make the conditions of (1) temperature of interior of apparatus, (2) amount
of moisture bought into the apparatus by the incoming current of air, and (3) the
rate of combustion of alcohol approximately alike at the beginning and at the end
of each experiment. These periods were six hours or more each. The experiments ,
proper began at the end of the first period and ended at the close of the second


m : :iii .i







31


VOLATILE ORGANIC COMPOI'()UNS.
It has been found necessary in experiments with some animals, e. g.,
oxen, to determine the quantities of carbon in the hydrocarbons and
other volatile organic compounds given off' from the body. Of these
the most important appears to be marsh gas produced by the ferment-
ative action of bacteria in the large intestine. Witl meni the quantity
of such compounds produced is apparently very small. They were not
determined in the experiments here reported, although it will doubtless
be necessary to look for such compounds and perhaps to determine
quantitatively their content of carbon and hydrogen in experiments
where the greatest accuracy is sought.

THE EXPERIMENTS.

The factors involved in a complete metabolism experiment and in
what is commonly called a respiration experiment are fully explained
on page 7. For reasons already given, the account of the respiration
experiments here reported include only tle results of measurements of
the income and outgo of nitrogen and carbon. The factors actually
determined and reported are:
Income.-Food, drink, and their content of nitrogen, carbon, protein (N X 6.25), fats
(ether extract), carbohydrates (by difference), mineral matter (asl).
Outgo.-Respiratory products-carbon dioxide and its content of carbon.
Feces-nitrogen, carbon, protein (N X 6.25), fats (ether extract), carbohy-
drates (by difference), mineral matter- (ash).
Urine-nitrogen, carbon.
As above explained, the experiments here reported involved digestion
experiments. The results of the latter are included in the descriptions
which follow. The determination of the digestibility of the several nutri-
ents of the food was made in the usual way, by comparing the amounts
of protein fat, carbohydrates, and mineral matter in the food and feces.1
The results of the digestion experiments, however, misrepresent the
actual digestion of the food by practically the amount of the metabolic
products in the feces. The error, however, is not large, and, so far as the
respiration experiments are concerned, it may be left out of account
entirely, since the question is the balance of total actual income and
outgo of chemical elements and the metabolic products of the feces
are as truly a part of the outgo as the undigested residue of the food.

period, and covered generally from twenty-four to forty-eight hours. Thie determi-
nations of water in the three check experiments ranged from 100.1 to 100.3 per cent
of the theoretical amount. Improvements were also made in the arrangements for
the determination of the quantities of he;it given off by the body.
'See discussion of this subject in U. S. Dept. Agr., Office of Experiment Stations
Bul. 21, pp. 56-73.





I


-.ai







32

THE I) ET.
Iii these experiments the effort was made to have the conditions as
nearly normal as possible. To this end it was essential that: (1) The
diet be such as to agree with the subject, and (2) the quantities of-
nutrients lie such as to meet the actual needs of the body under the
conditions in which the subject was placed during the experiment.
To facilitate tile right choice of the diet, observations on the ordinary
diet of tile subject and a preliminary test of a number of days were
considered essential. Accordingly the subject was allowed to select
his own diet from a bill of fare limited only by the skill and appliances
for cooking available. Il this way the selection of food was made such
ats to suit the palate and not become so monotonous as to cause nausea
or any other derangement of the processes of digestion. Tile subjects
were inclined to take more food than was necessary for the rather
inactive life in the respiration chamber. It was important to provide
that the regiment during the experiment should be not only such as
would meet the actual needs as regards kinds and amounts of nutri-
ents, but should also be the same from day to day.
Thle latter point is especially necessary. The actual income for a
given day or a given number of days is the amount digested and
absorbed during that period. If the food varies from day to day there
is no convenient means of learning to what extent the proportions of
nutrients digested vary with the food. Or, to put it in another way,
with varying diet the coefficients of digestibility of the several nutri-
ents, protein, fats, and carbohydrates, may change and it will be
impossible to tell how much is digested from each day's ration uuless a
separate digestion experiment is made each day, which latter would
either reduce the period of each experiment to one day or involve very
considerable difficulties in tlhe separation of the feces for each day.
Furthermore, only part of the food taken on a given day is absorbed
and used in the body on that day, and it is impossible to tell just when
the period during which it is being used begins and ends. If, therefore,
the diet varies from day to day, there is no way to learn how the vari-
ation affects the amounts actually absorbed from the alimentary canal
and used by the body on the different days during and immediately
following the days when the changes are made.
These considerations bring out one of the chief sources of uncertainty
ill such experiments, namely, the impossibility of measuring exactly
tile amount of material actually taken from the digestive tract and
brought into use by tie body during a specified period. It seemed
that the error would be materially reduced, if not eliminated, by pro.
vidingg the subject with a uniform diet for a long period and letting tle
actual experiment be for a shorter period included within this longer
period. This gives an opportunity to utilize the longer period for a
digestion experiment, the results of which may be taken as a measure
of the quantities of nutrients taken upl and used during the metabo- ,
lism experiment.










33


In accordance with these considerations, the subject conmlmence-d a

specified regimen some days in advance of each experiment. To adjui st

the quantities of food materials, so as to secure the proper proportiolls

of nutrients, estimates were made in advance by use of the figures for

composition of American materials.' The exact amounts of protein,

fats, and carbohydrates were, of course, not learned until the analyses

were made. Fortunately, the actual composition as thus found was

very close to the advance estimates in every case.
Meals were eaten three times daily at regular hours, thus conforming

as far as possible to ordinary custom. Drinking water was allowed at

all times, the weight used and the temperature, however, being care-
fully noted. The freedom allowed in the selection of diet added, it is

believed, materially to the success of the experiment, although the
number of different materials made the analyses quite laborious.

Although the diet inl eacl experiment was comparatively simple, a

considerable number of food materials were analyzed. The composi-
tion of the various foods is given in the following table:

TABLE l.-Composition of food materials used in the experiments.


C'.






Beef, fried......... 1
......do............. 2
.....do............ 3
.....do ............. 4
Eggs, boiled.......
.....do ..------------ 2
.....do ............ 3
Butter ............ 1
.....do............. 2
.....dos............ 3
.....do............. 4
Cheeseaa......... I 1
.....doa ........... "2
Milke..............
.....do............. 2
.....do............. 3
....do.... ...... 4
Crackers, milk.... 1
.....do............ 2
Bread, rye ........ I
.....do ........... 2
Bread, white...... 3
.....do............. 4
.-...do..- .--- -- ----- 4






Bread, brown...... 4
Oatmeal........... 4
Beans, dri d.--...... 4
Potato a, boiled... 1
....do............. 2
.....do..-.......... 3
....do............ 4
Applesb............ ()
Peaches........... 3
Sugar.............. (c)


Per ct.
4.64
4.85
4.73
5.48
2.07
1.99
2.41
.14
.16
.14
.18
4.29
4. 07
.58
.54
.53
.53
1.78
1.61
1.47
1.43
1.31
1.48
.93
2.75
1.10
.35
.36
.37
.40
.04
.09


I I
be
c' I
.d D0



Per ct. Per ct.


21.24
23. 00
20.26
23.18
14.45
14.05
15.43
64.64
66.40
67.07
66.85
33.43
35.80
7.27
6.79
6.17
6.01
44.00
44.01
25.85
25. 63
25. 83
27.82
22. 27
41.15
11.37
8.00
9.54
9.68
9.77
5.59
4.87
42.06


3.35
3.43
2.91
3.46
2.25
2.42
2.55
9.69
9.69
9.78
9.89
4.88
5.26
.94
1.00
1.02
1.00
6.54
7.08
2.37
3.97
3.77
3.89
3.13
5.83
1.57
1.27
1.36
1.48
1.41
.78
.57
6.45


C



Per ct.
58.9
56. 4
60. 3
53. 5
73.3
72.4
69. 2
9.2
8.9
8. 1
8.9
44.1
39. 7
85. 9
85. 9
85. 9
86. 2
5.7
5. 5
39. 0
40. 4
39. 1
35. 6
47.2
8.9
72. 8
80. 8
76. 8
74.8
75. 8
86. 7
89. 3


oX



Per ct.
29. 0
30. 3
29. 5
34.2
12.9
12.4
15.1
.9
1.0
.9
1.1
26. 8
25.4
3.6
3.4
3.3
3.3
11. 1
10.4
9.2
9.0
8.2
9.2
5.8
I 17.2
6.9
2.2
2.3
2.3
2.5
.2
.6


. .. .. ....... .
I


aThese two samples of cheese became partially decomposed before the determinations of carbon,
hydrogen, and heats of combustion could be made. The figures for factors named have been calcu-
lated from the percentages of protein, fats. and carbohydrates by use of the factors 0.5:. 0.765, and 0.44,
respectively, for the content of carbon, and 0.07. 0.12. and 0 06. respectively, for Ihe hydrogen content;
the heats of combustion were calculated from the values previously found iu two similar samples.
b Experiments Nos. 3 and 4.
eExperiments Nos. 1, 2, 3, and 4.
ih-
I- U. S. Dept. Agr., Office of Experiment Stations Bul. 28.
2771-No. 44-3


SC
00




2696
2699
2704
2715
2695
2698
2705
4238
4239
4248
4249
4228
4237
4227
4240
4247
4250
2697
2701
2693
2708
2724
2727
2726
2723
2728
2694
2700
2708
S 2725
2709
2707
2722


-= 0
Cs
;. i



SPer ct.
1. O0




1.2
'......"







4.0
5.5
5.5
5.5
5.6
69.6
69.3
50.3
49.0
50.6
52.8
43.6
65.2
18.0
16.2
19.8
21.7
20.6
12.7
9.7
100.0
. 100.0


ris




Calories.
2.494
2.758
2.424
2.904
1. 897
2.043
2. 123
8.122
8.184
8.435
8. 169
3.800
4.219
.836
.822
.807
.798
4. 677
4. 679
2.681
2. 607
2.735
2.892
2. 305
4.409
1.179
.787
.905
1.032
.989
.547
.476
3.987


Per ct.
9.8
11. 1
8.1
10.4
11.3
13.0
13.2
86. 3
85.4
88. 4
86.9
24. 5
27.0
4.2
4.5
4.5
4.2
12.3
12. 2
.2
.2
1.3
1.4
1.2
7.0
.4
.1
.1
.1
.1
.2
.1


Per ct.
1.3
1.5
2.0
2.0
1.0
1.0
1. 1
3.6
4.7
2.7
3.1
3.4
3.9
.8
.7
.8
.7
1.3
2.6
1.3
1.4
.8
1.0
2.2
1.7
1.9
.7
1.0
1. 1
1.0
.2
.3
I.......







34

DAILY ROUTINE.
The digestion experiment which was made with each respirtion
experiment commenced two or three days before the latter, but both ..
ended at the same time. On the second or third day of the digestion
experiment the subject entered the respiration chamber, but, in order.
to insure normal conditions, the respiration experiment did not begin
until six hours after he had entered. This allowed the subject an
opportunity for arranging his furniture, the hygrometer, thermometer,
and other apparatus in the room, and permitted the establishment of
the needed equilibrium of temperature and moisture content in the
chamber preparatory to the respiration experiment itself.
The food and drink were passed in and the solid and liquid excreta
were removed through the food aperture in the side of the apparatus.
A comfortable temperature was maintained within the room by means
of a current of cold water, which passed through the pipes of the heat
absorbers inside the chamber and thus brought away the heat radiated
from the man's body. The temperature which best suited the feelings
of the subject, generally not far from 200 C., was maintained through.
out the whole of each experiment, except during one period of the last
experiment, when the subject was engaged in hard muscular work. In
this case a very large amount of heat was given off from the body, and
the current of cold water passing through the absorbers did not suffice
to prevent the temperature from rising at times to 230 or 240. As this
high temperature was maintained for only a few hours at a time, it is
clearly an exception to the rule.
The occupants of the chamber passed the time in such ways as were
in general most agreeable under the circumstances. They observed
regular hours of eating and sleeping. There was, of course, almost no
opportunity for exercise. In the last experiment, however, a special .~
arrangement was made for vigorous muscular labor in lifting and
lowering a weight suspended from a pulley. This arrangement will
be described in connection with the other details of the experiment.
Abundant opportunity was given for reading, considerable converse.
tion was held between the occupant and the men who did the work out-
side, and the monotony was also relieved from time to time by visitors.
Since the experiments went on day and night, relays of the force for
day and night work were, of course, necessary. During the day a
force of five or six persons was generally employed. During the night,
when the occupant of the chamber was asleep, the force was reduced
to three.
A brief description of the routine of one day will perhaps help to a
better understanding of the way in which the experiment was carried
out. The night force of operators was relieved at 7 o'clock a. m. At
that time the subject was awake and ready for breakfast. The assist- |
ant, who had charge of the preparation and cooking of the food, pre..i
pared the breakfast; the chemist of the night force changed the system:i.l




-.""fi Iil:


35

of U-tubes for analysis of the air. The day chemist proceeded to start
the passage of the air through the fresh system of tubes, and then
weighed the system which had just been removed; the readings of the
meter by which the ventilating current of air was measured, and of
temperature, barometric pressure, etc., were made. The subject, hav-
ing emptied the bladder at 6 a. m., passed out the liquid, and at the
same time the solid excreta. The readings of the hygrometer and
thermometer inside the apparatus were taken by the subject on rising,
and the observations were repeated once in two hours throughout
the day. Naturally, the inquiry regarding the subject's physical con-
dition, and any changes needed, received early attention in the morning.
Breakfast was ordinarily served at about half past 7 o'clock, dinner at
about half past 12 o'clock, and supper at 6 o'clock. Drinking water
was given whenever desired, its weight and temperature being noted.
The freezing apparatus required repacking with ice and salt about
once in two hours during the day and night; the rate of flow of water
through the aspirators by which the samples of air for analysis were
drawn was regulated every half hour. The temperature of the air of
the meter was recorded hourly. The freezers through which the outgoing
air passed were changed once in twelve hours, aud the water condensed
in them was weighed. The absorption tubes for the water and carbon
dioxid of the air samples were changed once in six hours, at which time
the temperature of the aspirators, the temperature of the meter, and
the readings of the meter and of the air-pump register were recorded.
Concurrently with all of these operations, the analytical work was
carried on and completed as rapidly as possible.

COMPUTATION OF RESULTS.
NITROGEN BALANCE.
Nitrogen in urine.-In the estimate of nitrogen balance the measure
of the nitrogen metabolized in the body during a given period is sought
in the nitrogen of the urine for a period of equal length. The period
is commonly a day of twenty-four hours. The period for collecting the
urine, however, can not be coincident with that for which the nitrogen
metabolism is to be measured, since some time is required for the metab-
olized nitrogen to be conveyed to the kidneys, passed into the bladder,
and afterwards excreted in the urine. The twenty-four-hour period for
collecting the urine must therefore begin and end later than the cor-
responding nitrogen-metabolism period of twenty-four hours. This
interval, during which the excretion of nitrogen lags behind the metab-
olism, may for convenience be termed the nitrogen lag." Unfortu-
nately there are few data for judging accurately as to the length of this
interval of lag. Indeed one of the most difficult problems in experi-
ments of this class is to determine the actual source of the nitrogen
Secreted in the urine-that is, to determine whether the identical nitro-
:gen of the food is excreted in the urine after a short interval, or





: : .i;; M; :i iiI,

36

whether the nitrogen becomes part of the body tissue and an equiva-
lent amount (derived from the body) is excreted.
Kolpakcha1 has recently made some interesting experiments with
dogs which bear on this problem. He compared the ratio of phospho.
rus and nitrogen and sulphur and nitrogen in the food- and urine under
various dietary conditions, and also when no food was consumed. These
ratios were found to vary under the different dietary conditions. The
conclusion was reached that when the food supply was adequate very
little nitrogenous tissue was broken down, i. e., the nitrogen excreted
actually came from the food. An excess of protein eaten over the
amount required was stored up inside the cells of the protein tissue of
the body, but was not immediately made a part of the actual tissue.
It was simply reserve material. After a few days of fasting, this
reserve was exhausted and the body was then compelled to draw on its
own protein. Since the above-mentioned period is short, the conclusion
seems warranted that in the case of dogs the actual nitrogen consumed
in the food is soon excreted under ordinary conditions.
In the present experiments a lag of six hours was assumed in one case
and a lag of twelve hours in another. The fluctuations in the daily
excretion of nitrogen in the experiments herewith reported when the
diet and other conditions were reasonably uniform indicate, however,
that it is impossible to make any accurate estimate of this interval of
lag. These fluctuations are shown in the statistics of the nitrogen
excretion in Tables 5, 12, 19, and 26.
It is a familiar fact that some materials may be excreted by the urine
within a very short time after they have been taken in the food. Thus
it is a common observation that the peculiar odor of urine which comes
from asparagus may be observed within an hour after eating the latter.
In several rough tests made in this laboratory very small quantities
of potassium iodid were administered to a person, and a perceptible test
for iodine was obtained in the urine within half an hour after taking
the salt.
Such observations as these, however, do not give exact indications
of the rapidity of secretion and excretion of metabolized nitrogen.
Thus it was found, in experiment No. 4 (p. 51), where the metabolism
of nitrogen was materially increased by severe muscular work during
a period of three days, that the increase of nitrogen in the urine appar-
ently lagged a day behind the period of increased muscular exercise,
and after the muscular work stopped there was a similar lag in the
return of the nitrogen of the urine to the previous level of muscular
rest. In this case, however, the data do not exactly define the time of
rise and fall of nitrogen secretion or excretion. If the urine had been
collected and its nitrogen determined every six hours instead of mixing lte
the amount collected for twenty-four hours together and making but a


SPhysiologichekii Sbornik., 1 (1888), p. 56.


_____




. ...--- - ---- r S- ----------------------


S37

single analysis, as was actually done, the results might have given a
closer indication of the relation between the times of increased and
decreased metabolism and those of increased crease n creased excretion
of nitrogen.
The experiments here reported were divided into experimental days
of twenty-four hours. These experimental days were not calendar
days beginning at midnight, but were made to begin at such hours as
were most convenient. In experiment No. 4 the nitrogen was col-
lected and examined during twenty-four-hour periods, each beginning
and ending six hours after the corresponding experimental day. The
arrangements and calculations for experiments 1 and 2 were somewhat
different from those for experiments 3 and 4, as explained on page 49.
The principal factors involved in the computation of the nitrogen
balance may be stated as follows:
(1) Nitrogen of food.-This represents the gross income.
(2) Nitrogen offices.
(3) Nitrogen of urine.-This is mainly the nitrogen of compounds from the food
and body tissue which have not been completely oxidized, the most important being
urea.
Nos. 2 and 3 together make up the gross outgo of nitrogen.
(4) Nitrogen of food digested and absorbed and thus made available for use in the
body. This is the total nitrogen less that of the feces. Its amount is found by sub-
tracting No. 2 from No. 1. It may be designated as "total available" nitrogen, i. e.,
the total available for metabolism.
(5) Nitrogen gained or lost by the body.-If more nitrogen is taken into the body
than is given off-in other words, if No. I is greater than the sum of Nos. 2 and 3, or,
what is the same thing, if No. 4 is greater than No. 3-the difference will be the
amount the body has gained. If, on the other hand, the body has given off more
nitrogen than it has received, the difference, No. 3 less No. 4, is the amount lost. It
is customary to multiply the amount gained or lost by 6.25 and to assume that the
product represents the gain or loss of protein.

CARBON BALANCE.

In like manner the principal data involved in the computation of the
carbon balance may be succinctly grouped as follows:
(1) Carbon of food.-This is the gross income.
(2) Carbon of feces.
(3) Carbon of urine.
(4) Carbon of carbon dioxide exhaled.
Nos. 2, 3, and 4 together make up the gross outgo.
(5) Carbon of food digested and absorbed and thus made available for metabolism.
It if found by subtracting No. 2 from No. 1, and may be designated as total avail-
able" carbon, i. e., total available for metabolism. The carbon of the metabolic
products of the feces is here treated as if it were a part of the undigested residue
of the food.
S (6) Carbon actually utilized.-This is the carbon absorbed less that excreted by
the kidneys in the form of urea and other products of incomplete oxidation of
organic compounds. It is found by subtracting No. 3 from No. 5, and may be desig-
nated as "net available" carbon, 1. e., the total amount available for building tissue
or yielding energy.







38


(7) Carbon gained or lost by the body.-If No. 1 is greater than the anm of No. ,3,
and 4, or, what is the same thing, if No. 5 exceeds the sum of Nos. 3 and 4, the d41f-
ferrlnce will represent the gain in carbon. If, on the other hand, the body has lost
carbon, the amount will be founil by subtracting No. 5 from the sum of Nos. 3 al4d
GAIN AND 1,RSS O( PROTEIN AND FAT. ..1
The method usually followed in these computations is the one origl-
nally proposed by Pettenkofer and Voit and used by them and other
Sexperimienters. It assumes that the nitrogen, carbon, and hydrogen :
gained or lost by the body belongs to either protein compounds, fats,
i* or carbohydrates, and that these have definite proportions of nitrogen,
carbon, and hydrogen. On this basis the quantities of these three
elements gained or lost would serve as data for computation ot the gain
or loss of each one of the compounds.
()f course these assumptions are not entirely accurate, but they are
enough so for our present purpose. Even if they were accurate it
would be impossible to tell exactly how much of either class of com-
pounds was actually metabolized and actually- stored in the body or
resolved into its constituents and given off from the body. It would
only be possible to estimate the difference between the total amount
of eacl substance which was stored and the total amount which was
broken up and burned. As regards the protein stored or lost, it is
impossible to tell how much belongs to either cell tissue or cell contents,
or how much has simply formed a part of the blood or other fluids.
The case is entirely analogous with the fats and carbohydrates. But
*it seems fair to assume that the increase or decrease of nitrogenous
material will be mainly that of the proteid compounds, which belong
properly to connective and contractive tissue, and inasmuch as the
proportion of nitrogen in all these is approximately 16 per cent, the
quantity of protein gained or lost during the experiment corresponds
to very nearly 6.25 times that amount of nitrogen. With the nitrogen
of protein is a certain nearly constant amount of carbon. It is easy,
therefore, to compute the amount of the latter element which is either
stored by the body or lost from the body in protein. The algebraic ni
difference between the protein carbon gained or lost and the total car-
bon gained or lost represents the carbon gained or lost in carbohydrates
and fats. If we had the balance of hydrogen, or, better, the balance
of hydrogen and oxygen, and could assume definite quantities of car-
bon, hydrogen, and oxygen for the carbohydrates and fats, it would be
easy to calculate the amounts of these and of water actually gained or
lost. It is, however, common to assume that the quantity of carbohy- i.|
rates in the body, which is very small, is not materially changed,and
that consequently the carbon gained or lost outside of that in the pro-
tein belongs to f at. Accordingly the gain or loss of carbon outside
that belonging to the protein gained or lost is taken as representing ..
Sthe quantity of fat gained or lost. In calculations here used it is
assumed that the protein contains 16 per cent of nitrogen and 53 per
cent of carbon, and at the t count 7.5 per cent of carbon.

cerlt "" cabnad ht h ll nnnl~il~ ~i5 ~r

... "l.







39

The method of computation may be expressed algebraically as follows:
Let the amount of gain or loss of nitrogen be represented by N and
the amount of gain or loss of carbon by 4- C. Then:
1 N x .25 = protein gained or lost = P
S- P x 0.53 = carbon gained or lost in protein = C (protein)
C C (protein) = carbon stored or lost as fat = C (fat)
C (fat) + 0.765 = fat gained or lost.

ENERGY.
S The potential energy of tlie ingredients of food is commonly estimated
by the use of the factors proposed by Rubner,' which assign 4.1 calories
to each gram of protein or carbohydrates and 9.3 calories to each gram
of fat. This figure for protein, however, represents a net fuel value,
and is obtained by subtracting from the total fuel value of protein,
taken as 5.5 calories per gram, the value for the nitrogenous compounds,
Including urea, not completely oxidized.
In the experiments here described the heats of combustion of the
food materials, feces, and dry matter of urine were determined directly
by the use of the bomb calorimeter, as above stated. T'he figures given
in the tables, therefore, represent the results of these determinations
rather than estimates made by the use of factors. In the computations
of energy of the protein and fat gained or lost from the body, however,
it is, of course, necessary to use factors. For protein gained or lost
the factor 5.5 was employed. For the fat gained or lost the factor 9.4
was used as representing the heat of combustion of human fat per gram.
The principal data involved in these computations may be classified
as was done with those of nitrogen and carbon above.
(1) Total energy of nutrients of food, or total energy of income. This is represented
by the heats of combustion of the food materials.
(2) Energy in feces, actual heats of combustion.
(3) Energy in urine, heats of combustion of (dry matter.
(4) Total energy in food digested and absorbed.-This is usually found by subtracting
No. 2 from No. 1, and may be designated as total available energy. This value obtained
by difference, however, does not exactly represent the fuel value realized from the
digested food, for the reason that there is always a portion of digested food which
is not completely oxidized-namely, the organic matter, mainly nitrogenous, which
is secreted by the kidneys and excreted in the urine. Assuming the organism to be
in nitrogen equilibrium, the heat of combustion of this partially oxidized material
may le assumed to be that of the water-free substance of the urine. For the diges-
tion experiment, in which the gain and loss of body material are left out of account,
it is most convenient to estimate the fuel value of this partly oxidized nitrogenous
material and subtract it from the total heat of combustion of the digested food.
For this purpose it is assumed that the whole will be in the form of urea, and that
the amount of the latter will correspond to the amount of digested nitrogen.
S (5) Net energy of food digested and absorbed.-If protein is neither gained nor lost,
the net energy is found by subtracting No. 3 from No. 4. If protein is stored, No. 3 is
too small by the value of the urea and kindred compounds corresponding to the
Nitrogen in the protein stored. If protein is lost, No. 3 is too large by the energy of
SZtschr. Biol., 21 (1885), p. 250.







4 0 ..........

the urea which comes from the protein lost. The fuel value of urea correapol idiiugi
to 1 gr:nm of protein is 0.87 calories.'1
If, then, the protein stored or lost is multiplied by 0.87 and the product added to
No. 3 when protein is stored and subtracted from it when lost, the energy of the
urine corresponding to the protein digested is obtained. In other words, the net !,
energy of the food digested is No. 4 (No. 3 + 0.87 X protein gained or lost).
It is extremely probable that further consideration of the subject, together with
investigations 1now contemplated, may lead to more or less change in the details of
the method here eiiployed for the cstim:rtion of cnergy'of the compounds in queal
tion, including especially the nitrogenous compounds. This method will, however,
sullice for the present use, which is only tentative.'
(I) Energy liberated as heat or meanifeslrd as crternal Imsnclar work.-If a balance of
energy is to be made, another factor must be taken into account, namely, the heat
r:adiateld from the body, and that equivalent to the external muscular work per-
formed. Though this was measured in the present experiment, for the reason
alreadyy stated, the results are withheld, and the balance of income and outgo of
energy is not given.
RESPIRATION EXPERIMENT No. 1 (DIGESTION EXPERIMENT No. 11).
The subject in this experiment was a Swede 29 years of age who
acted as lIoaborory janitor and was accustomed to a moderate amount
of muscular work. lie would be called a hearty cater. During the
progress of the experiments he read a little for diversion, but the
larger part of the time was as free from mental and physical activities
as practicable. While he was entirely willing to do everything that
was required of him, it became evident that he did not find the sojourn
in the chamber entirely agreeable. Toward the end of the second
experiment lie became somewhat ill, but the circumstances were such
that it could hardly be attributed to impure air or any other abnormal
condition; indeed, there seemed to be good ground to believe that the
slight illness was caused by nervousness due to the sojourn in the res-
piration chamber and an undefined and unfounded fear that some
trouble might result.
The diet was comparatively simple. It was of his own selection'
and was made up of such foods as he would have eaten under ordinary
conditions. Three meals a day were eaten. Water was consumed ad
'Urea, CON2H,, contains 46.67 per cent of nitrogen; consequently Nx2.143=urea.
From the values obtained by Berthelot, Stohmann, and others, the fuel value of urea
may be taken as 2.53 calories per gram. Assuming that all of the digested protein
is consumed in the body to urea, we can find the theoretical value of the urea cor-
responding to 1 gram of protein as follows: Weight of protein 6.25= weight of
nitrogen. Weight of N X 2.143 = weight of urea. Weight of urea X 2.53=heat of
combustion of urea. Or the heat of combustion of the urea corresponding to 1 gram
2.143 x 2.53
of protein is 6.25 =-0.87 calories. The subject of metabolism of energy is dis-..
cussed in U. S. Dept. Agr., Office of Experiment Stations Bul. 21, p. 113.
SRuhner, Ztschr. Biol., 21 (1885), p. 337. The results of the present experiments,
both those given beyond and others still unpublished, agree entirely with Rubner's
in showing that the heat of combustion of the dry matter in the urine is much
larger than that of the urea, which would correspond to the nitrogen in the urine.









41


libitum. The foods consumed at each meal are shown in tie following
table:

TABLE 2.-Daily menu, respiration experiment No. I (digestion experiment No. 11).


Breakfast.


i-
S Eggs, about.............
Bu tter..................
Milk ..................
Bread .................
Sugar ...................
Coffee, about ............


Gram a.
100
15
100
100
20
300


Inner.


COoked meat ...........
Butter..................
Milk .................
read ..................
Potatoes................


Gramin.
121
20
300
150
150


Supper.


(r ams.
CbheRe ................. 75
ilk ................... 60oo
Milk crarkers .......... 10


The digestion experiment was of longer duration than tile respiration
experiment. It began with breakfast February 15, 1896, and ended

with dinner February 19, covering four and two-thirds days and includ-
ing 14 meals. Of this period two and one-fourth days (11 a. m. Feb-
ruary 17 until the close of the experiment) were passed in the respira-

tion chamber. The weight of the subject (without clothing) at the
beginning of the latter period was 66.9 kilograms (147O pounds). The

total amount of each food consumed and of the feces excreted during
the whole experimental period, the composition and fuel values of food

and feces, and the amount and percentage of each nutrient digested are
shown in Table 3.


TABLE 3.-Food eaten and digested during the whole experimental period, 41 days (diges-
tion experiment No. 11).


Labo-
ra-
tory
num-
ber.


2696
2695
4238
4228
4227
2697
2693
2694
2722

2764


Kind of food.


Beef, fried......................
Eggs, boiled ....................
Butter................-........
Cheese ........................
Milk .......--- ..-...-...-.......
Crackers, milk .................
Bread, rye...................
Potatoes, boiled.................
Sugar..........................

Total.......................
Feces .........................

Amount digested..........
Fuel value urea .................


Weight
for
experi-
ment.


Grams.
604
497
175
300
4, 400
396
1, 250
755
100

.......02
102


Total
organic
matter.-


Grams.
240
127
153
158
582
368
746
140
100

2, 607
71

2, 536


Net amount digested ...... ....................
Per cent digested................ .......... 97.3


Protein
(N x 6.25.)



Gram s.
175
64
2
80
159
44
115
17

656
26

630

..........


Fat.



Grams.
59
56
151
74
183
48
2
1

574
15

559


.........
97.4


Carbo-
hydrates.



Grams.
6
..........
4
240
276
629
122
100

1, 377
30

1,347


..97.......
97.8


Fuel
value.
deter-
mined.


Calories.
1,506
943
1,421
1,266
3, 678
1,852
3, 351
594
399

15,010
500

14, 510
535

13,975
93.1


a.V


-m 19







42

The amount, composition, and fuel value of the food during the two..
and one-fourth days (February 17, 11 a. m., to February 19, 5 p. a.)
passed in the respiration chamber are shown in the following table:
TABLE 4.-Food eaten during the period in the respiration chamber, 2J days (r"wpfrafdwf
erperiment No. 1).
Labo. Ie i valus.
ra Ki Weight N Citrn. Protein Ca -
. KKind 4f d. wprday. gent' na. 6.25.) t v ~ l .
HUM.rn-.m DetI- Ft
1-r. mined. Iated.

Oneh day.. ? mral. I
Gram, ira. Grant. raim. Girams. Grams. irrans. CWalrik. OCorif.
2696 Beef. frid--------.......... 121 5.61 25.70 35.1 11.8 1.3 302 30
2695 Eggs, boiled......... 2. 14.16 12.7 1 41. 6 ....... 11 11
423 IButter .............. 35 .05 22.6r' .3 30.2 .... 284 MM
4228' hewse ............... 75 3.22 25.07 20.1 18.4 | .9 2185 s
4227 Milk........ ......... 1,000 5.80 72.7' 36.3 41.5 I 54.5 8396 I
2697 Cra'kers, milk....... 100 1.78 44.00 11. 1 12.3 69.6 46 4
2693 Bread, rye........... 250 3.67 64.62 23.0 .4 125.8 670 461
2694 Potatoes, boiled ..... 150 2 12.00 3. .2.2 24.3 118 11
2722 Sugar ................ 20 ....... 8.41 ................. 20.0 80
Total............... 22.68 289.28 141.8 125.9 296.4 3,229 3.173
For dinner, Feb. 19.
2696 Beef, fried............. 120 5.57 25.49 34.8 11.7 1.3 1 29 39
4238 Butter ............... 20 .03 12.93 .2 17.3 ......... 12 1 I
4227 Milk ................. 300 1.74 21.81 10.9 12.4 16. 3 251 2a
2693 Bread, rye............... 150 2.20) 38.77 13.8 .2 75.4 402 387
2694 Potatoes, Iuiled ...... 150 .52 12.00 3.2 .2 24. 3 118 11
Totl .... ..... .... 10.06 111.00 1 62.8 41.8 117.3 1,23 1,217
CGraid total, 21
days ......... ........ 55.42 689.56 349.2 293.6 710.1 7, 90 7,

On the days which the subject passed in the respiration chamber the
urine was collected also. In this and the following experiment it was
not collected after the subject left the apparatus.' The urine was col-
lected from 6 p. m. on the day before the respiration experiment began
to 5 p. m. on the day the experiment ended. As the experiment began
at noon, the weights of urine excreted have been recalculated so as to give
the weights from noon to noon, instead of from 6 p. m. to 6 p. m. In
doing this it was assumed that the amount secreted was uniform from
hour to hour, and that the amount for the original period, from 6 p. m.
to 6 p. m., could be divided into two parts proportional to the time, one
part being the amount from 6 p. m. to 12 m. the next day, the other
the amount from 12 m. to 6 p. m. The amount for the short period of
six hours, from 12 m. to 6 p. in. of one day, was then added to the amount
for the longer period of eighteen hours, from 6 p. m. to 12 m. of the
following day, thus giving the total weight for the twenty-four boars
from 12 m. to 12 m. Of course, this allows for no "lag in the urine
(see page 35), but the error thus introduced is probably not very great.
The subject had been doing light manual labor before entering the
apparatus, and did no work during the experiment. There may have
been a slightly larger amount of nitrogen in the urine of the first day
of the experiment than was actually metabolized during that day.

'In experiments 3 and 4 it was collected for some time after, as stated in the
descriptions of those experiments.









43


. Such excess might have Deen due to tile metabolizing of a larger
quantity of nitrogen during the day before the subject entered the
. apparatus. Thus it is to be observed that the weight of nitrogen
Eliminated in all of the experiments, with tihe exception of the third,
I is slightly smaller on the second lday tlian on tie first.
The amount of urine and feces excreted while the lsuljet was in the
respiration chamber and the nitrogen alnd carbon content and fuel
value of each are given in the following table:

TABLE 5.-Nitrogen and carbon and fuel alne of urinr and feren ( respiration e.peri-
ment No. I).


Urine and feces.



Urine (February 17-18, 12 m. to
12 m.)....-.......-----....----
Urine (February 18-19, 12 m. to
12 m.)....----..----...----.....
Urine (February 19, 12 m. to 5
p.m.) ........................
Toted...-..................
Feces (average for 1 day) .......
Total, 2 days....................


Amount..



Gramsi.
1,395
1,313
260
2,968
21.9
43.8


Nitrogen.


Eni I
Carbon. vi~'ie per
gratiu.
iram


Per ct. Grains. Per ec. Irams. ('alnries.
1.45 20.23 0.84 11.72 0. 110
1.45 19.04 .84 11.03 .110
1.45 3.77 .84 2.18 .110
.... 43.04 .... 24.93 .........
4.14 .91 41.01 8.98 4.903
........ 1.82 ........ 17.96 .........
"i-


T-lal
fuel
value.


I'alories.
154
145
28
327
107
214


The carbon dioxid produced by the subject was measured during the
period passed in the respiration chamber. For convenience in collect-
ing samples the day of twenty-four hours was divided into several
periods. The volume of air passing through the respiration chamber,
the amount of carbon dioxide it contained per liter on entering and on
leaving the chamber, and the total amount excreted by the subject, as
well as the total amount of carbon in the excreted carbon dioxid are
shown in the following table:

TABLE 6.-Carbon dioxid produced in respiration experiment No. 1.


Date.


February 17, 12m., to
February 18,12 m.


February 18, 12 m., to
February 19, 12 m.
February 19, 12 -n. to
5 p.m.


Period.


12 m. to 7 p. m.....
7 p.m. to2 a.m....
2 a. m. to9 a. m....
9 a. n. to 3 p.m...
3 p.m to 10p.m...
10 p.m. to 4 a. m..
4 a. m. to 11 a. m...
l1 a. T. to 5 p.m...


Ventila-
tion (vol-
Snme of
air).


Liters.
21,724
21.094
20,566
20,052
20, 300
19,450
21,227
17,938


CO, per liter.


In incom- In outgo-
ing air. ing air.


Mg.
0.51
.61
.59
.58
.58
.58
.60
.59


Mg.
12.48
10.28
8.01
12.21
13.39
9.75
9. 30
12.74


Given
off by
subject.

Mg.
11.97
9.67
7.42
11.63
12.81
9.17
8.70
12. 15


aThe air in the respiration chamber at the close of the experiment contained more CO- than at the
beginning. Analyses ot samples, knowing the volume of air in the chamber, showed this difference
in amount to be approximately 60.4 grams. It is assumed that this increase took place during the
first twenty-four hours, on which assumption 60.4 grams of CO, exhaled remained in the apparatus,
and hence was not deducted and measured by the regular analyses. Accordingly thia amount of COs
is added to the amount found by the analysis for the first twenty-four hours.
bOf the period'from 9 a. u to 3 p.m., half belongs to the first and half to the second day of the
experiment.
cOf the period from 11 a. m to 5 p. m.. the first hour belongs to the second day and the remainder to
the fraction of the third day of the experiment.


Labo-
ra-
tory
num-
ber.

5016






2764


Total
weight C
exhaled
in CO.,.


Total
weight
CO,ex-
haled by
subject.

Grams.
Sa 60.4
260.0
203.9
152.7
f 116.6
I 116.6
260. 4
178. 4
184.7
36. 31
S181.6f


5


Grams.

216.1



211.7

An i


7


4a. i


~___









44

From the data of Tables 4, 5, and C the balance of income and outgo
of carbon and nitrogen is computed with results shown in Table 7.
In this and in the following experiment the subject passed two and
one-fourth days (fifty-four hours) in the respiration chamber, and the
nitrogen of the urine and the carbon of the carbon dioxid exhaled
were determined for this length of time. The number of meals taken,
however, was seven, which iIncluded two whole days and dinner on the
third day. It is, of course, impossible to say how much of the nutri-
ents a:ud energy of the food eaten for dinner at 12 o'clock would be
utilized in the body before the close of the experiment at 5 o'clock.
There is aI similar uncertainty as to how much of the outgo of feces
should be accredited to this quarter da.y. Accordingly, the results of
these two experiments have been calculated for the two whole days,
the fraction of a day at tle close of the experiment being left out of
account.

TA'iI.I: 7.-I-alance of income and outgo of nitrogen and carbon (respiration expert
mCen No. 1).


Date.


February 17-18, 12 m.
to 12 n..............
February 18-19, 12 m.
to 12m............
Total, 2 days...


In
food.



Gms.
22.7
22. 7


Nitrogen.


In In
urine. feces.



Gms. (Gmo.


20. 2
19.0


0.9


45.4 39. 2


Gain.


Gms.
1.6
2.8
I 4.4


Carbon.


In
food.


Gms.
289.3
289.3
678.6


In In
uriie.i feces.



Gms. GOmn.
11.7 9.0
11.0 9.0
22.7 18.0


In res-
pira-
tory
prod-
ucts.


Gms.
216.5
211.7
428. 2


Gain.


Gms.
52. 1
57.6
109. 7


Fuel value.

I I


Of
food.


OCalo-
ries.
3,29p
8.229
6,458


Of IOf
urine. I fhees.


Calo-
ries.
154
145
29


As explained on p. 38, the amount of protein gained or lost by the
body may be computed from the gain or loss of nitrogen, and the amount
of fat stored or lost by the body may be computed from the gain or loss
of carbon, taking into account also the carbon in the protein gained or
lost. The results-of such computations-are given in the following table:

TABLE 8.-Gain or loss of protein and fat in respiration experiment No. 1.


Date.


February 17-18,12 m. to 12 m......
February 18-19, 12 m. to 12 in......
Total, 2 days................


Nitrogen
gained. .


Grams.
1.6
2.8
4.4


Total car.
Protein bon
gained. gained.


Carbon in
protein
gained.


Grams. Grams. Grams.
10.0 52.1 5.3
17.5 57.6 9.3
27.5 I109.7 14.6


iAlgebraic
difference be-
tween total
carbon and
carbon in' pro-
tein (=M).

Gramn.
46.8
48.3
95.1


Fat
gained
( 0.765).


Grams.
6L2
63.1
IA.3
2124.3


The table indicates that during the two days of the experiment 27.5
grams of protein and 124.3 grams of fat were stored up in the body.


ries.
107
107
214


1-


-- --- ~ --- I










45

RESPIRATION EXPERIMENT No. 2 (DI(;ESTION EXPERIMENT Ni. 12).

This experiment was made with the same subject and under the same
conditions as experiment No. 1. The digestion experiment began with
breakfast February 24, 1896, and ended with dinner February 28, mak-
ing 14 meals, or four and two-thirds days. The period from 11 a. m.,
February 26, to the close of the experiment, at 5 )p. m., February 28,
covering two and one-fourth days, and including 7 meals, was spent in
the respiration chamber. The weight of the subject at the beginning
of the experiment (without clothing) was 67.5 kilograms (1484 pounds).
The daily menu was as follows:


TABLE 9.-Daily menu, respiration experiment No. 2 (digestion experiment No. 12).


Breakfast.


Eggs, about.............
Butter...............
Milk ..................
Bread ................
Sugar ..............
Coffee, aboat............


Grams.
100
15
100
100
20
300


Dinner.


Cooked meat.........
Butter ................
M ilk ..................
Bread ...............
Potatoes ..............


Supper.


Grains.
121
20,
300
150
150


Cheese ................
Milk ..................
Milk crackers..........
Sugar ..................
Coffee, about...........


Tables 10 and 11 show the amounts, composition, and fuel values of
the food and feces and the coefficients of digestibility for the whole
period (four and two-thirds days) and the amount, composition, and
fuel value of the food during the period in the respiration chamber
(two and one-fourth days).

TABLE 10.-Food eaten and digested during the whole experimental period, 4' days
(digestion experiment No. 12).


Kind of food.


Beef, fried......................
Eggs, boiled...--..............-.
Butter .........................
Cheese......................
Milk ............................
Crackers, milk..................
Bread, rye.....................
Potatoes, boiled.................
Sugar ...........................
Total......................
Feces .........................

Amount digested..........
Fuel value urea.................

Net amount digested......
Per cent digested...............


Weight
for
experi-
ment.


Grams.
515
498
175
300
2, 400
400
1, 136
661
180

.........

.---------.
..........

..........
..........


Total
organic
matter.


Grams.
217
127
151
169
321
368
661
146
180

2,340
81

2, 259


Protein
(N X 6.25).



Grams.
160
62
2
76
81
42
102
30
..........

55
46

509


96.5 91.57


Fat.


Carbo-
hydrates.


Grams. Grams.
57 .........
65 ...........
149 .........
81: 12
108 132
49 277
2 557
1 115
.......... 180

512 1,273
15 20

497 1,253

9........ ........
97.1 98.4


Grams.
75
100
100
20
300


Labo-
ra-
tory
num-
ber.


2699
2698
4239
4237
4240
2701
2703
2700
2722

2765


Fuel
value,
deter-
mined.


Calories.
1,436
1,017
1, 432
1,266
1,973
1, 872
2,961
638
718

13,313
542

12,771
448

12,323
92.6









46


TABLs 11.-Food eaten and digested during Ith period in Ith respiration chamber, 3s a ,
(respiration erperimenut Vo. ).


Labo-
ra-
tory

ber.



2699i
2698
4239
4237
4240
2701
2703
2700
2722


Weight
Cr.


Grainms.
121
101
35
75
500
100
228
150
40


Nitro-
gen.



iramra.
5.87
2.01
.06
3.05
2.70
1.67
3.26
.54


Carbon.




Grams.
27.83
1. 10
23. 24
26.85
33.95
44.01
58.44
14. 31
16.82


I'rotein i L
(N .6.25 F). a



Grams. 'Gramas.
30.7 13.4
12 6 13.1
.3 29.9
19.1 20.3
16.9 22.5
10.4 12.2
20.4 .5
3.4 .1
.......... ........


Carbo-
hy-
drateo.


Grams.
0.9

3.0
27.5
68.5
111.8
29.6
40.0


Kind of food.



(hOe day, 3 mmmas.

Beef. fried.............
Eggs, boiled..........
Butter ..............
Cheese...............
Milk ................
Crackers, milk.......
Bread, rye ...........
Potatoes, boiled ......
Sugar ................

Total...........

For dinner, Feb. 8S.

Beef, frile............
But er ..............
M ilk .................
Breadn rye....-.......
Potatmoe, boiled......

Total..........


31 I1.50
20 .03
300 1.62
80 1.14
61 .22

........ 4.51


Grand total, 2.
days..................


42.83


7.13
13. 28
20.37
20.50
5.82

67.10

588.20


9.4
.2
10.1
7.2
1.4

28. 3


267.9


3. 4 .2
17.1 1........
13.5 i 16.5
.2 39.2
........ 13.0

34.2 I 68.9

258.2 631.5


Fuel valae.


Deter-
mined.


otleries.
337
SM

817
411
488
54



U
1645



247
208
59

764


6.612


m



I.
it'
4g5

141
81L




S84
10

7S
61



q, o


The amounts of urine and feces excreted during the period in the
respiration chamber and the nitrogen and carbon content and fuel
value of each are shown in the following table:


TABLE 12.-- itrogen and carbon


and fuel ralue of urine
mnent No. 3).


and feoe respirationn empri-


Labo-
ra-
tory
n um-
ber.


Urine and feces.


5018 Urine (February 26-27, 12 m. to
12 m.) .......................
Urine (February 27-28, 12 m. to
12 m.).......................
Urine (February 28, 12 m. to 5
p. m .)......... ..............

Total.....................
2765 Feces averaget for I day) .......
Total, 2 days..................


Amount.



Gramvs.
969


Nitrogen.


Per ct. Grams.
1.9,2 18. 60


913 1.92

190 1.92


2.072
23. 8
47. 6


6. 65
........


17.53

3.65


I I:I~L


39. 78
1.58
3.16


........I 19.16 260.55 119.8j 112.0 281.3


2609
42'39
4240
2703:1
2700


Carbon.


Fuel
value per
gram.


lorie*
0.19


.18
.1 le


Per ct.
1.52

1.52

1.52


Gramis.
14. 73

13.88

2.89


31.50
9.87
19.74


Total
fel



lerims.
11


830

232


41.49


4.886.




.. ........ .


47


The carbon dioxid produced during the period in the respiration

chamber is shown in the following table:

TABLE 13.-Carbon dioxid produced in respiration experiment No. 2.


Date.


February 26.12 m., to
February 27,12 m.


February 27,12 m., to
February 28,12m.
February 28,12 m. to}
5 p. m.


Period.


12 m. tof6 p.nm.....
6 p. m. to 1 a. m...
1 a.m. to 7a.m....
7 a.m. to 2 p. m...
2 p. m.to9 p. m. ..
9 p.m. to 4 a.m....
4a. m to 10.30 a. m.
10.30 a. m. to5 p. m.


Ventila-
t ion
(volume
of air).


Liters.
21,064
20,932
20,686
21, 880
22,492
22,900
22,216
21,607


CO, per liter.


In incom-
ing air.


Mg.
0.56
.57
.59
.60
.54
.60
.61
.58


In outgo.
ing air.


My.
11.63
11.50
8.06
11.20
12.65
8.45
9.16
10. 02


Given
of' by
subject

Mg.
11.07
10.93
7.47
10.60
12.11
7.85
8.55
10. 34


Total
weight
CO2 ex-
haled by
subject.


Total
weight C
exhaled
in CO2.


I Grams. Grams.
I 53.2 )
S 233. 2
228.8 227.8
154.5
{ 165.6
S266.3 I1
272. 3
179.8 207.3
190. I
52.11 46.18
171.3 46. 8


I The air in the respiration chamber at the close of the experiment contained more CO2 than at the
beginning. Analyses of samples, compared with the volume of air in the chamber, showed this
difference in amount to be approximately 53.2 grams. It is assumed that this increase took place
during the first twenty-four hours, on which assumption 53.2 grams of CO2 exhaled remained in the
apparatus, and hence was not. deducted and measured by the regular analyses. Accordingly, this
amount of CO, is added to the amount found by the analysis for the first twenty-four hours.
:Of the period from 7 a. m. to 2 p. m., five hours belong to the first, and the remainder to the second
day of the experiment.
SOf the period from 10.30 a. m. to 5 p.m., the first one and oie-half hours belong to the second
day and the remainder to the fraction of the third day of the experiment.

Table 14 shows the balance of income and outgo of nitrogen and car-

bon. The figures are computed from data given in Tables 11, 12, and 13.

TABLE 14.-Balance of income and outgo of nitrogen and carbon (respiration experiment
No. 2).


Date.


February 26-27, 12
m. to 12 m.......
February 27-28, 12
m.to 12 m.......


Total, 2 days.I


Nitrogen.


In
food.


Gms.
1-9 .


In In
urine. feces.




Gins. Gma.
iA i i 6


Gain
(+)or
loss




Gms.
1 Ob


J. Z a 0U. J. j.
19.2 17.5 1.6 1 +0.1

38.4 36. 1 3.2 -0.9


Carbon.


In
food.




Gm s.
260.6


In In
urine, feces.


Gms.
14.7


260.6 13.9

521.2 28.6


Gms.
9.9

9.9

19.8


In res-
pira-
tory
prod-
ucts.


Gms.
227. 8

207.3

435. 1


Gain
(+) or
loss




Gins.
+ 8.2
+29. 5

+37.7


Fuel value.


Of
food.



Calo-
ries.
2, 924

2, 924

5,848


Of Of
urine, feces.


Calo-
4e1 9


ICalo-
0-ISO


7r "". IF.
164 116

154 116

318 232


The calculated gains or losses of protein and fat are shown in Table 15.

TABLE 15.-Gain or loss of protein and fat (respiration experiment No. 2).


Date.


Nitrogen
gained(+)
or lost(-).


Grams.
February 26-27,12 m. to 12 m ... -1.
February 27-28, 12 m. to 12 m ... +0. ]


Total, 2 days..............


-0. 9


Protein
gained (+)
or lost(-).




Grams.
-6.3
+0.6

-5.7


Total
carbon
gained.


Gramins.
+ 8.2
+29. 5


Carbon in
protein
gained (+)
or lost (-).


Grains.
-3. 3
+0.3


+37.7 -3. 0


Algebraic
difference
between
total car-
bon andt
carbon in
protein
(=M).

Gramns.
+11.5
+29. 2

+40.7


Fat
gained
(0.
0.765).


Grams.'
+15.0
+38.2

+53.2


I


I


,

.


i








48

RESPIRATION EXPERIMENT No. 3 (DIGESTION EXPERIMENT No. 13).

In this experiment the methods had been considerably improved and.4
the force of observers enlarged, advantage being taken of the expe iiii
ence gained in the two previous experiments. The subject was aI
chemist (0. F.'T.) 24 years old. The experiment began with breakfast
March 13 and ended with breakfast March 21, 1890, thus covering eight
and one-third days and including 25 meals. The respiration experiment
proper covered the 5 days with 15 meals from 11 a. m. March 6 to 11
a. m. March 21, inclusive. The weight of the subject at the beginning
of the experiment (without clothing) was 57.2 kilograms (126 pounds).
The subject was accustomed to rather less muscular labor than the
subject of the first two experiments. lie was also rather lighter in
weight. During the experiment he performed as little muscular labor
as possible. He passed the time in resting, with light reading for
diversion. The diet, which he himself selected, was somewhat smaller
than that of the subject of the first two experiments and furnished
considerably less protein and energy.
The daily menu throughout the experiment was as follows:

TABLE 16.-Daily menu, respiration experiment No. S (digestion experiment YVo. 13).

Breakfast. Dinner. Supper.

Grams. Grams. Gramm
Eggs .................... 113 Cooked beef............ 95 Milk ...................
Butter ............... 10 Butter ............... 10 Bread .................. 1
Milk.-......--......... 100 Milk ......--.........--.. 60 Su ar..................
Bread .................. 75 Bread .................. 75 Peaches or pears....... 90
Sugar ................. 20 Sugar .................. 20
Apples................ .. 85 1 Potatoes .............. 130
Tea or coffee, about..... 300 Peaches or pears....... 150
Tea or coffee, about .... 300

The amounts, composition, and fuel values of the food and feces and :
the coefficientsof digestibility for the whole period (eight and one-third
days), and the amount, composition, and fuel value of the food for the
period in the respiration chamber (five days) are shown in the follow-
ing tables:
TABLE 17.-Food eaten and digested during the whole experimental period, 8 days (dAge-
lion experiment No. 13).

lbo-- Weight Total Fer-
try Kind of food. f r organic e Fat.
Dany dexperi- org o(N x6.25). hydrates. deter-
nur- meant. matter. mined

Grams. Grams. Granms. Grams. Grams. Oawrie.
2704 Beef, fried.......... .............. 766 289 227 62 --......-- .. ,857
2705 Eggs, boiled.................... 904 256 137 119 .......... I .l
4248 Butter .......................... 170 152 2 150 .......... 148
4247 Milk ............................ 5.380 717 178 245 24 4.8
2724 Bread ........................... 2,275 1,367 187 30 1,150 6,
2708 Potatoes, boiled.................. 2,300 554 52 3 4 9 3,W3
2709 Apples.......................... 755 99 2 1 96 641
2707 Peaches......................... 1.400 146 8 2 136 4
2706 Pears ...........---........--.. 1,400 277 3 1 273 1,]1*
2722 Sugar ........................... 400 400- ....- .....-.- ... 400. 1 .ii
Total................. ...... ......... .4,257 796M 1 613 2,8 M 1,


M *








49

TABLE 17.-Food eaten and digested during lthe whtlrle vIxprimental period, r'e.--Cont'd.

Labo- K Weight udlI I Fuel
ra- i'r l'rltuin t 'arlm- valll
tory Kind of i'food. lor r.nic .i Fat. irl-
Saext. i (N 6.25). iydrates. doter-
noaI- mattr. .
ber. Ieit. ned.

Grains. rants. fi rains. (drams. Grams. Calories.
2760 Feces ...............--........... 131 7 44 I 20 3:1 628
Amiount digested.................... 4. 1Uu 752 | 59:3 2815 21.313
Fuel value urea .................. ..........'.......... ........................ ..... 54
Net amount digueted ...... ................................. ............. 20.659
Per cent digested......................... 97.7 94.5 96.7 98.9 94.2


TABLE 18.-Food eaten during the period in the respiration chamber, .5 days (respiration
expt-rimnent No. 3).

Labo- I Fuel values.
r- WeightCarbo-
tory Kind of food. for ro- Carbon. rotu Fat. hv- D
num- 5 days. gen. (N A-6.25). drites. Deter- Calnu-
r.m- 5a drates. mined lated.
ber.

Five days, 15 meals.
Grams. Grams. Grams. rams. Grams.,Grams. Calories. Calories.
2704 Beef, fried ........... 481 22. 75 97.43 142.2 38.7 1........ 1,166 1,145
2705 Eggs, boiled ......... 502 12.10 77.46 75.6 66.3 i...... 1,066 1,032
4248 Butter ....--....-- .. 100 .14 67.07 .9 88.4 ........ 843 826
4247 Milk ................ 3,300 17.49 203.60 109.2 150.0 180.5 2,663 2,737
2724 Bread --.............. 1,375 18.01 355.10 112.9 18.0 695.4 3,760 3,644
2708 Potatoes, boiled..... 1,350 4.99 130.70 30.5 1.5 293.0 1,393 1,383
2709 Apples -............ 425 .17 23.76 1.0 .7 54.0 232 235
2707 Peaches .--.....-...- 700 .63 34.09 5.0 1.3 85.0 333 388
2706 Pears................ 1,050 .42 85.57 2.2 1.0 170.7 841 718
2722 Sugar.............. 230 ........ 96.74 ..... .......... 210.0 917 861
Total..-..-....... ..--- 76.70 1,171.52 479.5 365.9 1,688.6 13,214 12,969
Quantities per day .. ........ 15.34 234.30 95.9 73.2 337.7 2,643 2, 594

Table 19 shows the amounts of urine and feces excreted during the
period in the respiration chamber and the nitrogen and carbon content
and fuel value of each. In this table a 12-hour lag is allowed in calcu-
lating the urine and feces (see p. 35). In the light of the results
obtained in the succeeding experiment this seems to be more nearly
accurate than the 6-hour lag. The time allowed for lag is, however,
probably of comparatively little importance, as the diet and occupation
were very nearly uniform.

TABLE 19.-Nitrogen and carbon and fuel values of urine and feces (respiration experi-
ment No. 3).

Labo- I
Sra- Fuel Total
tory Urine and feces. Amount. Nitrogen. i Carbon. alueper fuel
num- gram. value.
her.
I i
5020 Urine (March 16-17, 6 a. m. to Grams. Per et. Grams. Per ct. Grams. Calories. Calories.
6a. m.) ....................... 974 1.30 12.66 0.89 8.66 0.101 I 98
Urine (March 17-18, 6 a. m. to
6a. m.)--..--....-----------...--.. 1,118 1.20 13.46 .89 9.95 .101 113
Urine (March 18-19, 6 a. m. to
6a.m.) ..................... 1,188 1.15 13.61 .89 10.57 .101 120
Urine (March 19-20, 6 a m. to
6 a. m.) .--................--.. 1,325 1.04 13.69 .89 11.79 .101 134
Urine (March 20-21, 6 a. m. to
6 a.m.) ....................... 1.526 1.00 15.22 .89 13.58 .101 154
Total .................... 6, 131 --..... 68.64 .54.55 .......... 619
2760 Feces (average for 1 day)....... 16.4 5.34 .87 41.94 6.87 4.796 79
Total,5 days.................... 81.9 ....... 4.37 ........ 34.33 ......... 395

2771-No. 4- 4










50 '


The amount of carbon dioxid produced during the period in the .s.

piration chamber is shown in Table 20.

TABLE 20.-C'arbon dioxid produced in respiration experiment No. 3.


Date.





March 16, 11 a. m., to
March 17, 11 a. rn.


March 17, 11 a. i., to
March 114, 11 a. m.


March 18. 11 a. m., to
March 19, 11 a. m.


March 19, 11 a. m., to
March 20, 11 a. m.

Mairclh 20, I1a. m., to
March 21, 11 a. m.


Period.


11 a.m. to 6 p.m...
6 p. Im. to 1 a. m....
I a.m. to 7 a. ....
7 a. to 1 p.m....
1 p. m. to8 p. m....
8 p. m. to 3 a. m....
3 a.m. to 9a.m....
9 a. m. to 4 p. m....
4 p.m. to 1l p.m...
11 p. m.to 6 a.m...
6a. m. to 1 p.m...
1 p. I. to8 p.m....
8 p. m. to 3 a.m....
3 a. in. to 10 a. mn...
10 a.m. to 6p. m...
6 p.m. to 2a.m....
2 a.m. to 11 a. ...'


Ventila-
tion
volumee
of air).


Liters.
37, 462
41, 500
37,360
36, 470
40,150
29, 620
27,470
31,500
30,830
30,330
30, 700
33, 210
33,930
33, 820
37,060
40,990
44,093


COU, r liter. Total
-- weight
In inom.n- In uutno- GIveu Cd .
ing sai. ing ar. ubjt subject.


Mg. Mg. f. Gramn.
0.57 7.57 7.00 28. S
.56 0.13 5 57 231.3
.55 4.61 4.06 151.6
.56 7.19 6.63 {
'82.6
.60 7.21 6.61 26.6
.57 6.86 6.29 186.
.62 6.88 6.26 17L91
.61 9.89 9..28 { 10.
.58 9.07 8.49 261.9
.63 5.87 5.24 159.0
.62 8.51 7.89 { 13.1
'69.2
.65 8.87 8.22 72. 9
.57 6.90 6.42 216.6
.53 7.04 6.51 220.2
.57 8.80 8.29
1268.8
.56 7.36 6.80 27L8.6
.52 6.54 6.02 265.5


I Of the period from 7 a. ni. to 1 p. m., March 17, four hours belong to the first and the remainderto
the second day of the experiment.
In like manner each experimental period is made to end at 11 a. m.. the amount of CO eliminated Is
the period in which the day ends being divided between that day and the next proportionately to th
time.

The balance of income and outgo of nitrogen and carbon, as computed
from the data given in Tables 18, 19, and 20, is shown in Table 21:

TAILE 21.-Balance of income and outgo of nitrogen and carbon (respiration aperisn
No. 3).


Date.


March 16-17, 11
a. m. toll a. i.
March 17-18, 11
a. m. toll a. m.
'March 18-19, 11
a. in. to 11 a. m.
Mat;irh 19-20, 11
a. m. to 11 a. m.
MaIrch 20-21, 11
a. m. to 11 a. m.

Total, 5 days


Nitrogen.


In In


food.


Gias.
15.3

15. 3

15.3

15. 3

15.3

76. 5


urine.




Urns.
12.7

13.5

13.6

13.7

15.2

68.7


In
feces.




.Gins.
0.9

.9

.9

.9
.9

4.5


Gain
(+) or
loss
(-).




+1.7

+0.9

+0.8


+10. 7
.-.u a


Carbon.


In
food.


Gmrs.
234.3

234. 3

234.3

234.3

234.3


In In
urine. feces.


Gims.
8. 7 i

9.9

10.6

11.8

13.6


G6.9
6.9


6.9

6.9

6.9


+3.3 1,.171. 54.6i 34.5


it res-
piura-
tory
prod-
ucts.


Gmis.
220.9

215.3

218. 8

222.9

221.7

1,099.6


Gain
(+) or
lose
(-).


Gina.
- 2.2

+ 2.2

- 2.0

- 7.3

- 7.9

-17.2


Fuel value.


Of
food.



Calo-
ries.
2, 645


2,645

2,645

2,645

13,225


Calo-
ric*.
986

113

120
IN
134
154

619


iaOO.

tOfyw


m.3



215.18










2271.
32L 7


riew.
Tm
19


19

79

7.

3A'


I


Of Of
ar sa feoe.m


!


--U. 8








51

The calculated rginis ;an loIsss (,1' protci alnd I fat are shown ill
Table 22:

TABLC 22.-G-ain or loss of protein and fat (respiration crperiment .uo. 3).


Date.


Algbl)raiti Fat
Nitgron Pr'otiin Total Carbon i dirence gainl
il l'ri **arbon prot"ei l between to-
g ined ga iner aied gaind Itol l carbon l
(+(-) () or (+) ir and carbon lt
lut(-). lost(-). st(). lost(-). in protein M
( r.M). 0.765).

Graunia. IGra mst. (Crams. ram. Irains. Grams.


March 16-17,11 a.m.toll a.m.--...... +-1.7 +--10.6 2.2 5.6 7.8 -10.2
March 17-18, 11 i. n. to 11 a. in........ +0.9 -- 5.6 + 2.2 + 3. 0 0.8 1.0
March 18-19, 11 a. n. to 1 aa. nm........ + 0.8 +- 5.0 2.0 + 2.7 "- 4.7 6.1
March 19-20,11 a.m. to 11 a. m........ +0.7 + 4.4 7.3 + 2.3 9.6 -12.6
March 20-21, 11 a.m.to1 a.m......... -0.8 5.0 7.9 2.7 5.2 -6.8
Total, 5 days.................... +3. 3 +20.6 -17.2 +10.9 -28.1 -36.7

RESPIRATION EXPERIMENT No. 4 (DIGESTION EXPERIMENT No. 14).

The last experiment was more detailed than the previous ones and
the observations were more thoroughly systematized. The subject
was a physicist (A. W. S.), 22 years old, and weighed (without clothing)
at the beginning of the experiment 69.9 kilograms (154 pounds). The
experiment began with breakfast March 19 and ended with dinner
April 4, thus covering sixteen and two-third days and including fifty
meals. During the twelve days beginning 3 p. m. March 23 and ending
3 p. m. April 4 the subject was in the respiration chamber. The twelve
days were divided into five periods, the first of one and five-eighths,
the fifth of one and three-eighths, and the others of three days' dura-
tion each. The first and fifth periods were preliminary and supple-
mentary. In these preliminary and supplementary periods thus reck-
oned as one the subject did not engage in any muscular or mental
work except such reading and very slight physical exercise as were
needed to pass away the time comfortably. For convenience in making
the calculations of income and outgo, it was assumed that the amounts
of ingredients of food and excretory products for the five-eighths
and three-eighths days, respectively, made up the corresponding pro-
portions of the total daily amounts. Of course this assumption does not
affect the other periods of the experiment. The second period, of three
days duration, was devoted to mental labor. The subject engaged for
eight hours a day or thereabouts in the active work of either caculating
results of previous experiments or studying a German treatise on
physics. The mental application was as intense as it could well be
made. The third period, likewise of three days' duration, was given
to nearly absolute rest. During this time the subject avoided muscular
and mental exercise so far as possible. During a larger part of the
time he reclined upon the bed. Of course it was impossible to avoid
all intellectual activity, but the amount was made as small as practi-
cable. The fourth period was one of intense muscular activity. A


111~







52 .

pulley was attached to the top of the chamber. Over this passed a
cord. One end of the cord was attached to a block of iron weighing i
5.7 kilograms (12.5 pounds); on the other end was a handle. This pro-
vided for active exercise, not only of the arms, but also of the legs and:
other parts of the body. The whole arrangement was quite similar
to some of the forms of apparatus very commonly used for gymnastic 1
exercise. With this the subject worked severely for eight hours on
each of the three days, so that at the end of each day's work he was
thoroughly tired. He perspired very freely during the working boors.
This period was followed by the final short period of rest.
In examining the detailed results of the experiments it was interest-
ing to note that whatever had been the occupation during the day a
period of 6 hours' rest was sufficient to bring the elimination of carbon
dioxid back to a normal quantity. Even after the large elimination of
carbonic acid which accompanied each period of hard muscular work,
amounting at times to 500 grams for six hours, the simple return to rest
was followed almost immediately by a return to the normal elimination
(see Table 27).
In the case of the elimination of nitrogen in the urine, however, the
increase consequent upon hard muscular work or its decrease when the
body was in a state of rest did not manifest itself until some hours
after the muscular work began or ended (see Table 26). In the calcula-
tions for Table 26 a period of six hours was allowed for the lag in the
urine. By consulting that table, however, it will be seen that the
increase of nitrogen in the urine following the hard work of March 31
did not manifest itself until apparently thirty hours later, and did not
cease for an equally long period after the close of active exercise on
the evening of April 2, during which time the body had been ip a
state of as complete inactivity as possible. This subject is referred
to beyond.
The character of the food consumed during this experiment is shown
in the following daily menu:

TABLE 23 -paily menu, respiration experiment No. 4 (digestion experiment No. 14).

Breakfast. Dinner. Supper.
I' {IL


Grains.
White bread ............ 75
Oatmeal................ 40
Beans ................-.. 120
Milk .................... 150
Butter .................. 15
Sugar................... 20


Grams. :Gr w.
Cooked beef............ 96 Milk ...................
Wlhitt bread ........... 75 Brown bread'.......... 3ss
Mashed potatoes ....... 100
Butter ................. 30 1
Appl................. 125


Tables 24 and 25 show the amounts, composition, and fuel values of
the food and feces and the coefficients of digestibility for the whole
period (sixteen and two-thirds days) and the amount, composition, ant
fuel value of the food for the period in the respiration chamber twelve
days).










53


TABLE 24.-Food eaten and digested during the whole experimental period, 16t days
(digestion experiment No. 14).


Labo-
ra-
tory Kind of food.
num-
ber.


Beef, fried .......................
Butter .........................
Milk ............. .........-.....
Bread, white ...................
Bread, brown................
Oatmeal......................
Beans..........................
Potatoes, boiled .................
Apples..........................
Sugar ..........................

Total.....................
Feces .........................

Amount digested..........
Fuel value urea ...............


Net amount digested....--... .......
Per cent digested ............... ..........


TABLE 25.-Food eaten during the


period in the respiration chamber, 12 days (respiration
experiment No. 4).


Kind of food.


Twelve days, 36 meals.

Beef, fried...........
Butter ................
Milk ..................
Bread, white ..........
Bread, brown..........
Oatmeal ...-.........--
Beans ................
Potatoes ..............
Apples ................
Sugar ...............


Weight
per day.


SI I :


Grams.
96
45
650
150
250
40
120
100
125
20


I I


Nitro Carbon.
gen.


Grams.
5.28
.08
3.45
2.22
2.32
1.10
1.32
.40
.05


Total.................... 16.22


Grams.
22.33
30.08
39.06
41.73
55.67
16.46
13.64
9.77
6.99
8.41

244.14


Protein.


Grams.
33. 0
.5
21.5
13.8
14.5
6.9
8.3
2.5
.3


101.3


Fat.


Grams.
10.0
39. 1
27.3
2.0
2.9
2.8
.4
.1
.2


Carbo-
hy-
drates.



Grams.


36. 1
79. 2
109.0
26. 1
21.6
20. 6
15.9
20. 0


84.8 1328.5


Fuel values.


Deter-
mined.


Calories.
280
368
519
434
576
176
141


Calcu-
lated.


Calories.
273
367
520
420
553
171
138


99 99
68 69
80 82

2, 741 2,692


Table 26 gives the amount of urine and feces excreted during the

period in the respiration chamber and the nitrogen and carbon content

and fuel value of each.

TABLE 26.-Nitrogen and carbon in urine and feces (respiration experiment No. 4).


Urine and feces.


Urine (March 23-24, 9 p. m. to
12 m.).
Urine (March 24-25, 12 m. to
12 m.).
Urine (March 25-26, 12 m. to
12 m.).
Urine (March 26-27, 12 m. to
12 m.).
Urine (March 27-28, 12 m. to
12 m.).


n





Gms.
596

772

815

1,230

1,600


Nitrogen.


Per
cent.
1.53

1.83

1.61

1.11

.79


Gmns.
9.12

14.09

13.12

13.71

12.64


Carbon.


Per
cent.
0.99

.99

.72

.72

.72


Gms.
5.90

7.64

5.87

S8.86

11.52


Fuel
value
per
gram.


Cal-
ories.
0.113

.113

.083

.083

.083


Total
fuel
value.


Remarks.


Cal-
ories.
67 lPreliminary
period, no
87 work.

68 ental work.

102 Mental work.

133


2715
4249
4250
2727
2726
2723
2728
2725
2709
2722


2761


Weight
for
experi-
ment.


Grains.
1, 654
765
10, 61l0
2, 55"
4,000
680
2,040
1,700
2,125
340


432

..........
..........


Total
organic
matter.


Grams.
738
673
1,384
1,616
2,022
609
516
393
279
340

8, 570
330


8, 240


S 96. 2


Protein
(N 6.25).



(I rams.
566
8
351
235
232
117
141
42
5


1,697
147

1,550



91. 3


Fat.



Grams.
172
665
445
35
46
48
7
1
4
..........

1,423
58


1,365


95. 9


Carbo-
hydrates.



Grams.


588
1, 346
1,744
444
368
350
270
340

5, 450
125


5,325


97.7


Fuel
value,
deter-
mined.


Calories.
4, 80:
6, 249
8, 459
7, 375
9, 220
2.998
2. 415
1,681
1, 162
1,356

45, 708
2, 049

43, 659
1,347

42, 312
92.6


Labo-
ra-
tory
num-
ber.


2715
4249
4250
2727
2726
2723
2728
2725
2709
2722


Lab-
ora-
tory
num-
ber.


-1


5022




5023









54

TABLr 26.-Nitrogen and carbon in urine and feces-Continued.


Urine and foces.


Lab-
ora-
tory
nuil-
Iher.










5025


5026


2761


1 7.
Ga, n


Nitrogen.



Per
ent. IMa.


1, 713 U. I7
1 107 1.12

1,422 .902

662 1.77

841 1.95
798 1.79
1,529 1.05
822 .65


13,907
25. 4
304. 8


11. 90

12.40

13. 08

11.68

16.40
14.29
16.13
5.34


...... 163.90
5.46 1.39
...... 16.64


Carbon.


Per
cent.
0.70

.76

.76

1.31

1.31
1.31
.73
.73


....40


Olms.
13.02

R.41

10. 81

8.67

11.02
10.45
11.16
6.00

119.33
10.52
126.20


Fuel
value
per
gram.


C(l-
oriea.

.089

.089
.151

.151
.151
.055
.055


.723
on


Total
fuel
value.


(I.
ories.
152

99

126

100

127
121
P4
45

1.311
120
1,440


Renarka,


INo work.



Maoualar
work.

Supplemen-
tary petod,
no work.


The amount of carbon dioxid produced during the period in the
respiration chamber is shown in Table 27.

TABLE 27.--Carbon dioxid produced in respiration experiment No. 4.


Period.


3 p.m. to9p.mi...
9 p.m. to 3 a. m....
3 a. m. to 9 a.nm....
9a.m. to 3 p.m....
3p.m. to9 p.m....
9 p.n. to3 a m....
3 a. m. to9 a.m...
9 a. m. to p. m....
3p.nm. to9 p.m....
9p.m. to3 a. in...
3 a.m. to 9 a.m....
9a.m. to 3 p.m....
3 p.m. to 9 p.m....
9p.m. to 3 a.m....
3 a.m. to 9a.m....
9a.m. to 3 p.m...
3 p. m. to 9 p. m....
9p.m. to 3 a.m....
3a.m. to9a.m....
9a.m. to3 p.m....
3 p. m. to 9 p.mi....
9 p.m. to3 a.m....
3 a.m. to 9 am ....
9a.m.to3 p.m....
3p. m. to 9 p. m....
9 p. m. to3 a m....
3 a. m. to 9a. m....
9 a. to 3 p. m....
3 p. m. t 9 p. m....
9 p.m. to3 a.m....
3 a. m. to 9 a. m....
9 a. m. to 3 p. m....
3p. m. to9 p.m.-..
9p. m. to 3 a. m...
3 an. to 9 a.m....


Ventila-
tion
(volume
of air).


Liters.
21,840
23,348
23, 666
20. 962
21,420
22, 288
21,370
21,350
21,970
21,060
21, 370
21,240
22, 110
20 760
21,470
20, 760
21,780
22, 190
21,010
20,600
21, 220
21,520
20, 350
20,650
21,290
20, 790
20,350
21,320
21,290
21,976
20, 354
21,040
21,240
20, 750
20, 240


I Each experimental day ended at 6 a. m.: their
9 a. m. is diviilwL equally between the two days.


CO, per liter.
In Given
In incom-i In outgo- off by
ing air. ing air. subject.


Mg.
0.62
.59
.58
.58
.59
.57
.56
.55
.60
.62
.54
.56
.59
.56
.55
.56
.57
.55
.56
.58
.60
.57
.59
.63
.59
.55
.56
.58
.60
.61
.55
.58
.61
.58
.72


Mg.
10.48
9.42
8.12
12.76
11.89
9.05
9.29
12.77
11.96
10.34
8.71
12.28
11.44
9.47
8.76
10.96
11.05
9.05
9.01
11.32
12.52
11.31
9.23
12.30
11.60
9.51
9.57
12.20
10.72
10.88
11.45
21.09
20.37
11.20
9.94


Mg.
9.86
8.83
7.54
12. 18
11.30
8.48
8.73
12.22
11.36
9.72
8.17
11.72
10.85
8.91
8.21
10.40
10.48
8.50
8.45
10.74
11.92
10.74
8.64
1L67
11.01
8.96
9.01
11.62
10. 12
10.27
10.90
20.51
19.76
10.62
9.22


before the amount of CO, in the period from 3 a. m.


Urine (March 28-29, 12 in. to)
12 in.).
Urine (March 29 31, 12 m. to
12 m.).
I Urinle (March 30-31, 12 m. to
12 nii.).
IUrine (March 31-April 1, 12 m.
to 12 m.).
{ Trine(April 1-2,12m. to l2m...
Urine (April 2-3. 12 m. to 12m.)..
I Urine (April 3-4,12m. to 12 m.)..
Urinu (April 4,12 m. to 9 p. m.)..

Total......................
Feces (average for 1 day)......
Total...........................


Total
weight C
exbaleo
n CmO,.
mGwm.


130.2


237.0








231.1
}nt,$


In1,,


Date.


March 23, 3 p. m., to
March 24, 6 a. m.

March 24, 6 a. m., to
March 25, 6 a. m.


March 25, 6a. m., to
March 26, 6 a. m.


March 26, 6 a. m., to
March 27, 6 a. m.


March 27, 6 a. m., to
March 28, 6 a. m.


March 28, 6 a. m., to
March 29, 6 a.. .


March 29, 6 a. m., to
March 30, 6 a. nm.


March 30, 6 a. m., to
March 31, 6 a. m.


March :11, 6 a. m.. to
April 1, 6 a. m.


I.


Total
weight
CO, ex-
haled by
subject.

Grams.
214.9
206.3
189.3

255.2
242.2
189.1
{ 193.2
193. 3
260.8
249.6
204.8
'87.3
187.3
248.9
239.9
184.9
188.2

215.8
228.2
188. 7
1 88.8
'88.8
221.4
252.9
231.2
S'87.9
'188.0
240.9
234.5
186.2
191.7
1'91.7
247.8
215.5
225.8
S'110.9
S110.9
431.6
419.6
220.6
'f 193.3
' 193.4


22ILT



240.6


saR





-


MALr


n r r


!


I


1




r


55.


TABLE 27.-Carbon dioxid produced in respiration experiment No. 4-Continued.


Date.


April 1, 6 a. m., to
April 2, 6 a. ni.



April 2. 6 a. m., to
April 3, 6 a. m.


April 3, 6 a. m., to
April 4, 6 a. m.

April 4, 6 a. m., to
April 4, 3 p. in.


Period.




9 a. m. to 3 p.m....
3 p.in. top 9 1.m....
9 p. ni. toi 3 iL. in....
3 :. in. to a. in....
09:. m. to 3 p. 1i....
:I p. m. to9 p. i....
9 p. ni. to 3 a. in....
3 a. n. to9 a. im....
9 a. m. to 3 p. ni....
3 p. m. to9 p. mn....
9 p. ni. to 3 ai. il....
3a.m. to 0 a. inm....
9a. i. to 3 p. m....


I entila.
(v illtrI

Io air).


Liters.
21. 2911
21, :130
21,330
20, 82K)
19, 390
19. 972
21,400
21,941
20, 820
20, 686
21.360
21,125
20.575
21,268


(C', per liter

In incoin.' In outgo.


ing air.


M.y.
II. 65
.63
62
.71
.61
.65
.83
1.55
.83
.87
1. 2:1
1.94
.57


ing ir-.


MIy.
24. 18
22. 73
11.36
10.94
23.92
24. 62
11. 39
10.27
11.86
13.40
11.29
10.86
12.44


T'otall
weight
(iven CO ex-
(ot 13y lialded iby
nlhlject. Aublject.

MJi. Grains.
23. 53I 50. 9
22.10 471.4
10.74 246. 0
10.23 '99.
23.31 465.6
2:1.97 512.9
10. 5 21. 6
8.72 I '90.8
190.8
11.03 228.2
12.53 266.8
10.00 212.4
8.92 191.8
11.87 252.5


IEach experimental day induled at 6 a. m.; the
9 a. m. is divided equally between tho two (lays.


reform the amount of CO., in the period f'roni 3 a. ni. to


The balance of income and outgo of nitrogen and carbon made up

from data given in Tables 25, 26, and 27 is shown in the following
table:


TABLE 28.-Balance of income and outgo of nitrogen and carbon (respiration experiment
No. 4).


Date.


March 23-24, 9
p. m. to 12 m...
March 24-25, 12
m. to 12m.....
March 25-26; 12
m. to 12m.....
March 26-27, 12
m. to 13m.....
March 27-28, 12
m. to ]2 m.....
March 28-29, 12
m. to 12m ....
March 29-30, 12
m. to 12m.....
March 30-31, 12
m. to 12 m ....
March 31-April
1, 12 m. to 12 m
April 1-2, 12 m.
to 12 m.......
April 2-3, 12 m.
to 12 m.--.....
April 3-4, 12m.
to 12 m........
April 4,12 m. to
9p.m.........


Nitrogen.


In In In
food. urine, feces.


G-ms.
10. 1

16.2

16.2

16. 2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

6.1


Gms.
9.1

14.1

13. 1

13.7

12.6

11.9

12.4

13. 1

11.7

16.4

14.3

16.1

5.4


Gins.
0.9

1.4

1.4

1.4

1.4

1.4

1.4

1.4

1.4

1.4

1.4

1.4


Gain
(+)or
loss
(-).


Gina.

+0.1

+0.7

+1.7

+1.1

+2.2

+2.9

+2.4

+1.7

+3.1

-1.6

+0.5

-1.3


5 1+0.2


16.8 +13.7 '2,929.2


Carbon.


In
food.


Grams.
152. 6

244. 1

244.1

244.1

244.1

244. 1

244.1

244. 1

244. 1

244.1

244.1

244. 1

91.5


In In
urine. feces.


Gins.
5.9

7.6

5.9

8.9

11.5

13.0

8.4

10.8

8.7

11.0

10.4

11.2

6.0


Gmns.
6.6

10 5

10.5

10.5

10.5

10.5

10. 5

10.5

10.5

10.5

10.5

10.5

3.9


In res-
pira-
tory
prod-
ucts.


Grams.
139. 2

237.0

244. 3

231.6

220. 7

240. 6

229. 4

243.2

348. 0

384. 8

381. 8

242.7

93. 9


Gain
(+) or
loss
(-).



Grams.
+ 0.9

- 11.0

- 16.6

- 6.9

+ 1.4

- 20.0

- 4.2

- 20.4

-123. 1

-162.2

-158.6

- 20.3

- 12.3


Fuel value.


Of
food.



Calo-
ries.
1,713

2,741

2,741

2, 741

2,741

2,741

2, 741

2, 741

2,741

2,741

2,741

2, 741

1,028


Of Of
urine. feces.


Calo-

67

87

68

102

133

152

99

126

100

127

121

84

45


Calo-
ries.
75

120

120

120

120

120

120

120

120

120

120

120

45


126.0 3, 237.2 -553. 3 32, 892


STotal
weight C
ex haledl
in C(0,.


ra14.7
:184.7


381.7



242.7


93. 9


119. 3


d


-L


j


~ ---I~---


1-1---


1,311 1,440


Total,12dayasl94. 4 163.9I










56


The calculated gains and losses of protein and fat are shown in the
following table:

TABLE 29.-Gain or los of protein and fat (respiration experiment No. 4).


Date.


March 23-24,9 p. m. to 12 m.........
March 24-25, 12 m. to 12 m..........
March 25-26. 12m. to 12 in...........
March 26-27,12 m. to 12 m...........
March 27-28,12 m. to 12 m..........
March 28-29, 12 m. to 12 m...........
March 29-30.12 m. to 12 m..........
March 30-31,12 m. to 12 m...........
March 31-April 1, 12 m. to 12 m.....
April 1-2,12 m. to 12 m.............
April 2-3.12 m. to 12 m..............
April 3-4,12 m. to 12 m.............
April 4,12 m. to 9 p. m .............
Total, 12 days................


Nitrogen
gained
(+) or
lost (-).


Gramns.
+0.1
+0.7
+1.7
+1.1
+2.2
+2.9
+2.4
+1.7
+3.1
-1.6
+0.5
-1.3
+0.2

+13.7


Protein
gained
(+) or
lost (-).


Grams.
+ 0.6
+ 4.4
+10.6
+ 6.9
+13.8
+18. 1
+15.0
+10.6
+19.4
-10.0
+ 3.1
R.1
+ 1.2


Total
carbon
gained
(+) or
lost (-).


(Grams.
+ 0.9
- 11.0
- 16.6
- 6.9
+ 1.4
- 20.0
- 4.2
- 20.4
-123. 1
-162.2
-158.6
- 20.3
- 12.3


Carbon in
protein
gained
(+) or
lost (-).


Gramse.
+ 0.3
+ 2.3
+ 5.6
+ 3.7
+ 7.3
+ 9.6
+ 8.0
+ 5.6
+10.3
5.3
+ 1.6
4.3
+0.6


Algebraic dif-
ference be-
tween total
carbon
and carbon
in protein
(=M).

Grims.
+ 0.6
18.3
22.2
10.6
5.9
29.6
12.2
26.0
-133.4
-156.9
-160.2
1.0
12.9


a.t





0.75).

+ .6
- 17.4
- asB.
-13.8
- a7.

-15.3
-3L a
- CS..
-176.
--i.l


+85.6 -553.3 +45.3 --50.6 -78.4


DISCUSSION OF RESULTS.

VENTILATION AND PRODUCTION OF CARBON DIOXID.

The observations regarding ventilation and the effects of the presence
of carbonic acid in large quantities are of decided interest. The incom-
ing air, which was ordinary fresh air from the outside of the building,
contained on the average from 0.5 to 0.6 of a milligram of carbon
dioxid per liter; in the outgoing air the amount of carbon dioxid aver-
aged about 11 milligrams per liter, though the variations from this-
amount were considerable. In the last experiment, especially, the dif-
ferences in bodily activity in the different periods were very large, and
the differences in carbon dioxid exhalation were correspondingly great.
The results are epitomized in Table 30, which shows the quantities of
air supplied and carbon dioxid produced in each of the four experi-
ments:

TABLE 30.-Amount of carbon dioxid produced in the respiration apparatus.


Subject.


Janitor (E. O.)........
..... ................
Chemist(0. F. T.)....


Physicist (A. W. S.)..


Average. 12 days .....


Occupation.


SAmounts of COper liter
Dora- Air in outgoing air.
tion of plied
rpei- per Mini- I MarI Aver.
.minute. : um. mum. I age.


Daya. 'Liters.
Rest............ 2 49
.....do .......... 2 1 50
Light mental 5 75
work.
Rest............ 1. 55
Mental work.... 3 55
Rest ............ 3 55
Muscular work. 3 55
Rest............ ]j 55

.................. 12 55


Mg. Mg.
8.0 13.4
8.1 12.7
4.6 9.9

8.1 12.8
8.7 12.8
9.0 12.5
9.9 24.6
10.9 13.4

8.1 24.6


Me.
11.0
10.4
7.4
10.2
10.5
10.9
16.9
11.8

12.1


Experi-
ment
num-
ber.


Average

bourn.
ofOrams.
givsi off




7u.6
flagr
meunr
sa8~


I


I I


I







57


The table shows that the quantity of carbon dioxid in the incoming
air was normal, ranging from 0.55 to 0.60 milligrams per liter. The
ventilation in experiments Nos. 1 and 2 was at the rate of about 50
liters of air per minute; the carbon dioxid in the outgoing air varied
from 8 to 13.4 and averaged 10.7 milligrams per liter.
In experiment No. 3, with an average ventilation of 75 liters of air
per minute, the range of carbon dioxid in the air was from 4.6 to 9.9
milligrams per liter and the average 7.4 milligrams per liter. The
smaller quantity of carbon dioxid in the air as compared with experi-
ments Nos. 1 and 2 was due to the larger ventilation, since the average
weight of carbon dioxid given off in twenty-four hours was 848.9 grams
as compared with 778.6 grams in experiment No. 1 and 794.6 in experi-
ment No. 2. In these experiments the subject was either at rest or
engaged in light mental work or reading.
Experiment No. 4 is of much more interest in this connection, since
the differences in mental and physical exercise were much wider.
During the first and fifth periods of one and five-eighths and one and
three-eighths days, respectively, the subject was at rest. During the
second period, which lasted three days, he was engaged in rather severe
mental work. The third period was one of as nearly absolute rest as was
practicable. In the fourth period the subject was engaged in severe
muscular work for eight hours per day. The rate of ventilation was
55 liters per minute. The temperature of the air in the chamber was
generally from 190 to 200 C., though it fell at times to 170 and rose
during the periods of hard muscular work to 220.
The weight of carbon dioxid given off in twenty-four hours ranged
from about 850 to 900 grams for the days at rest and was no larger with
mental work, but averaged over 1,360 grams for the days of muscular
work. During two periods of six hours each of hard muscular work
the elimination of carbon dioxid reached 513 and 501 grams, respec-
tively. During the night, or sleeping period, the exhalation of carbon
dioxid was singularly constant irrespective of the day's occupation. It
amounted to 175 grams in six hours, with but slight variation from that
figure.'
The weight of carbon dioxid in the outgoing air during the periods
of rest and mental work ranged from 8.1 to 13.4 milligrams per liter,
but averaged not far from 11 milligrams per liter. During the period
of muscular work, however, the range was from 9.9 milligrams per liter
in the hours of rest, e. g., at night, to 24.6 milligrams per liter in the
hours of severe work.
Authorities on ventilation commonly estimate the maximum of carbon
dioxid permissible in the air of inhabited rooms at one part per thousand
by volume, which corresponds to about 1.97 milligrams of carbon dioxid
'For recent observations of the variations in the amount of carbon dioxide
excreted during sleeping and waking and under various conditions of work and
rest, see investigations by Sonden and Tigerstedt (Skand. Arch. Physiol., 6 (1895),
Nos. 1-3, pp. 1-224; abstracted in Experiment Station Record 8, p. 242).


L.







58

per liter. It will be observed that the amounts of carbon dioxid in the:
air in the respiration chamber during these experiments was from 8 to
25 milligrams per liter, and averaged 10 to 12 milligrams per liter. In
other words, the sulibects of these experiments lived constantly in an i
atmosphere containing from five to six times tihe amount of carbon dioxide
in the standard jst referred to. iin experiment No. 4 the carbon dioxide
rose to nearly thirteen times the amount in the standard.
The interesting fact in this connection is that no one of the sub-
jects appeared to experience any inconvenience whatever from either "ii
these large amounts of carbon dioxide or from any other products of I
exhalation.
The subject who remained in the apparatus during the five days of
the third experiment was as comfortable in every way, according to his
repeated statements both during the experiment and afterwards, as if
he had been in a room supplied with a larger amount of air. Even
in the fourth experiment the subject was not aware of the least incon-
venience or discomfort during the twelve days of his sojourn in the
chamber.
It may be added that these results are in accord with the late experi-
ments by Billings, Mitchell, and Bergey,' which imply that the discom-
fort experienced in poorly ventilated rooms is not due to the excess
of carbon dioxid. It seems probable, however, that one cause of the
discomfort felt in badly ventilated rooms occupied by a number of people
may be the large amount of moisture which accumulates in the air, while
at the same time the temperature rises. Some of the observations
made in the experiments above described accord with this hypothesis.
In anticipation of a special treatment of this phase of the experiments
in another place, further discussion is omitted here.
NUTRIENTS AND FUEL VALUES.
The nutrients and fuel values of the food eaten and digested in the
four experiments are briefly summarized in the following table:
TABLE 31.-Total and digested nutrients and fuel ralue of daily food in ithefous r spirs a
experiments.
In total food. In digested food.
Dura-
Exper- Dnra-
inet S Subject. of x- p Carbo. valuel, Pro- F- q i
tiher. pen-j tPro.:or d ataaP
K'1"' ?*"- tePi Fat. !h dalne- Fat. 1 hy- I
er. tein. draa deter- tein. d
mined. ima a !1
SaCal- Oi -
Days. Grams. Grans. Grams. ories. G rarm. Omrm., Gra. orsu. ,
1 Janitor (E.0.)... 2 142' 126 296 3,230 136 123 290
2 ....do............. 2 120 1 112 281 2,925 110 10 277 2.
3 Chemist (O. F. T.).. 5I 96 73 338 2.645 90 6 331 2.4L i
4 Physicist (A.W. S.) 12 101 85 329 2,740 93 62 321 .

a Fuel value of total food less that of feces and urine.
On the composition of expired air and its effect on animal life. Smithsonian Coi-,!!:
tributions to Knowledge, Vol. XXIX (No. 989, Hodgkine fund).
'Defren (Tech. Quart., 9 (1896), No. 2-3, p. 238; E. S. R., 8, p. 385) has Buggesti
that the deleterious effect of badly ventilated rooms may be due to the pres ftee t
nitrites, which he has found in considerable quantities in the air of such rooms.








59

The balance of income and outgo of nitrogen and carbon and the gain
or loss of body protein and fat in the four experiments are briefly sum-
marized as follows:

TABLE 32.-Balance of income and outgo of nitrogen and carbon and gain or loss of body
protein and fat in the four respiration experiments.

Nitrogen. Carbon. Pro- Fat.


Subject. _occpa- -
4 93 tion. +a I

I1 I

DTay. Oms. Gm.:s. G sGins Gm Gima. s.m Gims. Gms.
1 Janitor Rest.--. 2 45.4 39.2 1.8 + 4.4 578. 6 22.7 18.0 428.2 4-109.7+27.5+124.3
(E. O.).
2 ....do .... ..-..do... 2 38.4 36.1 3.2- 0.9 521.2 28.6 19.8 4:15.1 + 37.7 5.7 + 53.2
3 Chemist Light 5 76.5 68.7 4.5+ 3.31,171.5, 54.6 34.51,099. 6- 17.2+20. 6- 36.7
(O.F.T.). mental
work.
Rest.... 15 26.3 23.2 2.3+ 0.8 396.7 13.5 17.1 376. 2- 10.1-[ 5. 0- 16.6
Mental 3 48.6 39.4 4.2+ 5.0 732.3 26.3 31.5 696.6-- 22.1 +31.3- 50.5
work.
4 Ph it Resa ... 3 48.6 37.4 4.2 + 7.0 732.3 32.2 31.5 713.2- 44.6 4-43.7 88.6
ws M eusca- 3 48.6 42.4 4.2+ 2.0 732.3 30.1 31.5 1,114.6-443.9 +12.5-588.9
(A.W.5.). lar w'k.
Rent.--. 1 22.3 21.5 1.9- 1.1 335.6 17.2 14.4 336.6- 32.6- 6.9- 37.8
Whole 12 194.4163.9 16. 8 +13.7 2,929. 2119. 3126.0 3, 237.2 -555.3 +85.6 -782.4
exp't.


As explained previously, the total income is represented by the food
actually eaten (with drink and the oxygen of inhaled air), and the net
income by the total income minus the outgo in the feces, taking into
account also the incompletely oxidized material excreted in the urine.
The net income represents that part of' the food which is available for
the body. If the amount available is just sufficient for the needs of
the organism it will all be burned in the body to yield energy. If it is
insufficient some of the body tissue will be burned also, and if it is more
than sufficient some material may be stored. The nitrogen in the urine is
assumed to represent the nitrogenous material which has been (incom-
pletely) burned in the body. In the present experiments it is assumed
that the carbon in the urine is from the same source. The carbon of
the respiratory products is taken as representing the carbon which has
been completely burned.
In Table 33 are shown the nitrogen, carbon, and energy in the daily
net income and the material actually burned in the body in the four
experiments.








60

TABLE 33.-Daily net income and material actually burned in the body is the fair
ezperimenta.

Ex Dura- Digested food. Material burned in tha
pert- tion body.
menit Subject. Occupation. of ex- -
num. peri. i Nitro- Carbon. Fuel Nitro- Carbon. Fmel
ber. ment., gen. value. gen. a b value.

Days. (ranm. Grams. Calories. Grams. Orwan. O(sfie.
I Janitor (E.O.).... Rest........... 2 1. 281.. 3 2,970 19.0 225.5 2,310
2 ....do..................do ........ 2 17.6 250.7 2,650 8. 0 231.8 2,430
3 Chemist(O.F.T.). Light mental 5 14.4 227.4 2,460 13.7 230.9 2, 05
work.
rRet .......... 15 14.8 233.6 2,525 14.3 238.6 2.585
4 Phsicist (A.W. Mental work.. .3 14.8 233.6 2,520 13.1 241.0 2,6M
i. w. Rest.......... 3 14.8 233.6 2,495 12.5 248.4 2,I
SM sc lar work 3 14. 233.6 2, 505 14.1 381.6 4, 83
Reet.......... lj 14.8 2.3.6 2,540 15.2 260.2 2,87
Av. for 12 days... ............... ...... 14.8 233.6 2,510 13.6 279.7 318

a Nitrogen of urine, i. e., of incompletely oxidized nitrogenous material of food and body.
b Carbon of respiratory products plus that of urine.

In the first experiment the amount of protein was rather large. The
subject, a laboratory janitor, was accustomed to somewhat active mus-
cular work and had a very hearty appetite. The diet was of his own
selection and proved more than sufficient for the needs of his organism
during the experiment when he was comparatively inactive. His
organism stored both protein and fat.
In the next experiment, which was made with the same person, the
diet was the same in kind, but less in quantity. The ration proved
insufficient to maintain the nitrogen equilibrium, although some fat
was stored. In this case, however, the quantities of protein lost and
of fat gained were quite small, so that the organism was very nearly in
equilibrium, especially as regards nitrogen.
In the third experiment the diet was considerably smaller in protein
and energy than in the two preceding. The subject, a chemist, was
accustomed to rather less muscular labor than the subject of the first
and second experiments. He was also rather lighter in weight. The
diet which he chose was smaller in both nutrients and energy. The fig-
ures indicate a slight gain of protein and loss of fat during the experi-
ment, but on the whole the organism was very nearly in equilibrium in
respect to both nitrogen and carbon. The fuel value of the material
actually consumed in the body was larger than in either of the two
preceding experiments, though somewhat smaller than that in the fourth
experiment under similar conditions.
In the fourth experiment the subject was a physicist. He was taller
than the subject of the third and heavier than either of the subjects
in the preceding experiments. The diet was of his own selection, as
in the previous cases. The amount of nitrogen was less than in the
first two experiments, though slightly more than in the third. The
potential energy of the digested food was a little larger than in that
ot the third experiment. Nevertheless, the figures indicate a slight








61'

gain rather than loss of protein during all of the periods of the experi-
ment when there was no especially great muscular activity, though
there was constant loss of fat from the organisms. In the period of
muscular activity the loss of fat was very much larger, the loss of
carbon being 148 grams per day.
In discussing the gain or loss of protein the nitrogen lag is an impor-
tant factor. It has been stated above that in experiment No. 4 an
allowance of six hours was made for the lag of the urine. That this
time was insufficient was also pointed out, and thirty hours was sug-
gested as probably more nearly representing the period of lag. Table
34 gives the nitrogen and carbon in the net income and outgo for the
three important periods of this experiment, with the calculated nitro-
gen and carbon actually burned in the body and energy liberated,
allowing for both six hours' lag and thirty hours' lag.

TABLE 34.-Daily net income and material actually burned in the body, allowing for 6
hours' and 30 hours' lag of urine.

SNitrogen. Carbon.
3- Protein -- -
In na- gain In ma- Fat Fuel-
In i- trial Gain (+)or In di. trial loss. alue
Suggested burned ()Loss. loss.
o food. in the food. in the
body. body.

Allowing 6 hours'
lag: Days. Grams. Grams. Grams. Grams. Grams. Grams. Grams. Grams. Calories.
Mental work.-.. 3 14.8 13.1 +1.7 +10.4 233.6 241.0 7.4 16.8 100
Rest............ 3 14.8 12.5 +2. 3 +14.6 233.6 248.4 14.8 29.5 200
Muscular work 3 14.8 14.1 +0.7 +14.2 233.6 381.5 -147.9 -196.3 -1,820
Allowing30 bours'
lag:
Mentalwork.... 3 14.8 12.7 +2.1 +13.0 233.6 243.3 9.7 21.7 135
Rest ............ 3 14.8 12.4 +2.4 +15.0 233.6 247.0 13.4 27.8 180
Muscular work. 3 14.8 15.6 -0.8 5.0 233.6 382.4 -148.8 -191.0 -1,825


When the nitrogen lag is assumed to be six hours there is a small
gain of protein during the period of muscular work; but when it is
assumed to be thirty hours there is a small loss. When a thirty-hour
nitrogen lag is assumed the gains in protein during the periods of rest
and mental labor are somewhat larger than when a six-hour lag is
assumed.
It will be noticed that there are marked differences in the ways the
subjects in the four experiments utilized the food material at their
disposal. The differences in age, weight, occupation, and diet have
been referred to. It will, however, be of interest to add that some
studies had been previously made which throw a little more light upon
the dietary habits of two of them.
Two dietary studies were made in the family of the laboratory janitor,
one in February and the other in March, 1894.' In these the average
protein in the food eaten per man per day was estimated at 126 grams,
SSee Report of Storrs (Conn.) Agricultural Experiment Station, 1894, pp. 180 and 195.







62


and the total energy of the nutrients at 3,900 calories. The correspond-i
ing amounts digested were estimated at approximately 116 grams of:*
protein and 3,660 calories. This was, on the whole, a liberal diet. Itc.i
is slightly larger than the American standard' suggested for a man at-j
moderately severe muscular work.
Two dietary studies were made by the subject of experiment No. 4
:it his home in a country town in another State, on the occasions ao
vacation visits, one in the winter and the other in summer.' Therewas
but little difference between the results of the two. It seems fair to
assume that they may represent the dietary habits which the subject
had naturally acquired. The averages per man per day were approxi-
mately 79 grains of protein and 3,125 calories of energy. These quan-
tities are estimated to correspond to about 71 grams of protein and
2,955 calories of energy in the food actually digested.
It will be observed that, according to the above estimates, the labo-
ratory janitor, who was accustomed to moderately active muscular
work ten hours per day, and who was what would be called a "hearty
eater," actually burned during the first experiment 122 grams of the
136 grams of digestible protein in his food and at the same time stored
the remaining 14 grams, according to the calculations of these experi-
ments. Of the 2,970 calories in the food digested he burned material
corresponding to 2,310 calories. The digested nutrients of the food
furnished an excess of carbohydrates and fats as well as protein, so
that his organism stored fat and protein corresponding to 660 calories
of energy. In the second experiment his diet was reduced so as to
supply only 110 grams of digestible protein and 2,650 calories of energy.
In this case his organism was estimated to burn 113 grams of protein,
a trifle more than the food supplied, and 2,420 calories of energy. The
organism gained considerable fat, enough to make a gain of material
corresponding to 230 calories of energy.
The subjects of experiments Nos. 3 and 4, who were accustomed to
only light muscular activity, chose for their diet materials computed
to supply 90 and 93 grams of digestible protein, respectively, and other
digestible nutrients sufficient to furnish about 2,500 calories of energy
per day. In the respiration apparatus when at rest or engaged in
either light or severe mental work they burned in the body from 78 to I
86 grams of protein and from about 2,500 to 2,700 calories of energy. :
It was evident that this consumption must have been reasonably e6o-.iil
nomical, since the food in experiment No. 3 supplied only a trifle mori-::,
protein and a trifle less energy than was utilized; while in experimeua
No. 4, when the subject was at rest or engaged in mental work therl*
was with a slight apparent gain of protein a decided loss of fat. A1
though the subject of experiment No. 4 was a man of larger frame sa
greater weight than the subject of experiment No. 3, his o
SU. S. Dept. Agr., Office of Experiment Stations Bal. 21, p. 213.
"See Reports of Storr (Conn.) Experiment Station, 1895, p. 137, and 1896, p.




w"ii.


63

burned less protein; but this seems to accord with the results of dietary
studies mentioned above, which implies that he was in the habit of con-
suming small quantities of protein. While his organism burned smaller
Quantities of protein, it burned more fat and utilized more energy than
was the case with the subject of experiment No. 3. When the same
person engaged in severe muscular work the amount of protein burned
rose from 78 to 98 grams per day. At the same time the energy utilized
Rose from 2,695 to 4,325 calories. That there should be such an increase
Sin the amount of both protein burned and energy utilized with the
severe muscular work is not at all surprising. How the amount of pro-
tein burned during the period of muscular work would have been
affected if the quantity of carbohydrates and fats had been sufficient
to supply the needed energy is a question to be answered by further
experiment.
CONCLUSIONS.
The experiments above described offer considerable material for dis-
cussion. Since, however, they are of a preliminary character and are
to be followed by others in which the results of the experience here
obtained will be used, it is deemed best to reserve the discussion until
more of the anticipated work shall have been accomplished. Mean-
while the following statements are perhaps in place:
(1) The experience here obtained emphasizes the desirability of
longer experimental periods than have been customary in experiments
of this class. Although a considerable number of respiration experi-
ments have been made with animals and man, the periods have rarely
exceeded twenty-four hours. The figures in the tables above are suffi-
cient to show that the results obtained in periods so short are less con-
clusive than is to be desired.
(2) Much care needs to be bestowed upon the analyses of the mate-
rials of income and outgo. In the majority of experiments thus far
reported the composition of food and solid and liquid excretory prod-
Sucts has been in large part assumed, rather than estimated from direct
Analyses of specimens of the materials belonging to the experiments.
SIn like manner there is need of the greatest possible care and accuracy
in the determination of the gaseous excretory products. Nor can any
of the organic matters given off in perspiration and exhalation be left
out of account if the fullest accuracy is to be attained.
(3) It is to be hoped that future experience may lead to such
improvements as shall insure the accurate measurement of all the
chemical elements involved in the income and outgo. It is evident that
there are no insurmountable obstacles in the way of reasonably accu-
rate estimation of the income and outgo of nitrogen and carbon. As
regards the hydrogen, the difficulties of determination have thus far
been more serious, but they do not appear to be by any means insur-
mountable. The quantities of sulphur and phosphorus are so small
That extreme accuracy is needed for their estimation in order to insure








satisfactory comparison of income and outgo. The experience ..
in this laboratory since the experiments here described were m&adei..
cates that by refinement of methods reasonably reliable results m1iayi
obtained.
(4) The prospects for obtaining a satisfactory balance of income
outgo of energy are, on the whole, decidedly encouraging. The dete
minations of heats of combustion by the bomb calorimeter are emUe
nently satisfactory, and there seems to be good ground to hope tit
ultimately the measurements of heat given off from the body may alsO
prove sufficiently accurate for such purposes. Satisfactory results have.
already been reported by other experimenters with small animals and:
with men during experiments of short duration. Experience in this
laboratory since the above experiments were made have yielded results.
agreeing very closely indeed with the theoretical figures.
(5) The results of these experiments and of similar investigations
elsewhere bring out very clearly the difference in the amounts of nutri-
ents and energy required by the organisms of different persons anderi
different conditions, and confirm the results of previous inquiry in
showing that muscular labor is performed at the expense of the fats,
sugars, and starches. They also make it clear that the body may draw
upon protein for this purpose, although it has not yet been determined
just what are the conditions under which this is done. A large amount
of work will be needed to secure the experimental data necessary for
accurate generalizations. The importance of the subject is such as to
cal for the most extensive and painstaking research.








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