The composition of milk and cream, and their by-products

Material Information

The composition of milk and cream, and their by-products
Series Title:
Cornell reading-course for farmers. Series V, Dairying
Pearson, R. A
Place of Publication:
Ithaca N.Y
College of Agriculture, Cornell University
Publication Date:
Physical Description:
p. 401-416 : ill. ; 24 cm.


Subjects / Keywords:
Milk -- Composition ( lcsh )
Dairying ( lcsh )
Fats ( jstor )
Cream ( jstor )
Globules ( jstor )
non-fiction ( marcgt )


General Note:
Caption title.
General Note:
"December, 1904."
Statement of Responsibility:
by R.A. Pearson.

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1Reabing=ourse for farmers
S. W. FLETCHER, Supervisor.
SERIES V. ITHACA, N. Y., No. 22.

VERY household in the land uses milk. Practically every farm in
the land produces milk. To every one, therefore, any knowledge
that pertains to milk is of direct value. We may now inquire

FIG. 218. Student judging a dairy cow.
State of New York- Departmtent of Agriculture. /Frmers' ReadinhgCourse Bulletin No. 22.

What milk is; and this will involve a discussion also of cream, buttermilk
and other milk-derivatives.
1. Milk.
We could manufacture milk as well as we can make many other foods
if we could procure certain substances and mix them together as intimately
as is done by the cow. To make one gallon of milk we would have to use

52 ounces of fat.
3 ounces of casein.
I ounce of albumen.
6Y2 ounces of sugar.
I ounce of ash.
3 quarts, I pint and 7 ounces of water.
Many men have tried to discover an artificial method for making milk,
but thus far entirely without success. Perhaps they have forgotten that
the natural function of milk is as a food for the newly born and that it
is one of the most delicate substances found in nature. Indeed, not only
have they failed to make an artificial milk but they have failed also, in
efforts to make a good substitute for milk or for any of the products made
from milk.
Every one knows that milk is a fluid, white or yellowish white. A few
persons know that milk is heavier than water, but very few know anything
of its ingredients except that it contains more or less cream." Though
we do not expect to manufacture milk in any new way, yet it is useful
Sto know about it. Many points of interest are revealed to one who studies
it carefully.
Stated in percentages the composition of an average sample of cow's
milk is about as follows:

4. per cent fat.
2.6 per cent casein.
.7 per cent albumen.
5. per cent sugar.
.7 per cent ash.
87. per cent water.

But there may be considerable variation from these figures as will be
seen farther on. They are here given as round numbers which can
be easily memorized,


Milk is a little heavier than water. Its specific gravity varies from
1.029 to 1.035, the average being 1.032. This means that at a given
temperature 1,032 pounds of average milk will occupy the same space as
1,ooo pounds of pure water, therefore milk is 1.032 times as heavy as
water. Milk fat is lighter than water and this constituent tends to decrease
the specific gravity, but the other constituents are heavy enough to more
than overcome the effect of the light-weight fat.
When milk is examined through a high-power microscope it is seen to
consist of a clear fluid in which are floating many small round bodies of
different sizes. The floating bodies are globules of pure fat and the fluid
in which they are suspended is known as the milk serum. All of the fat
of milk is present in the form of these globules and the serum is made

Cream. Milk. Skimmed milk.
o o- 0

Sor watery part of the milk.
of all the other constituents viz.: water, sugar, casein, albumen and ash.

The constituents of the serum except water are called the solids not fat
and these together with the fat are known as the total solids of milk.
Fat.-From a commercial standpoint fat is by far the most important
constituent of milk. Great quantities of milk are bought and sold at prices
depending solely upon the "test, or the amount of fat. This is a fair

arrangement so long as the milk is of good sanitary quality. It is obvious

that the value of milk for butter-making depends upon its fat content
.because fat is the chief constituent of butter and tilhe amount of butter
that can be made frosope.m a given quantity of milk id bodies are fat globs in proportion t the
or watery part of the milk.

of all the of fat in the milk. The value of milk forr, sugar, casein, albumen and-making is also
indicated by constituents fat content. And the serum except water arise true alledin regard to milk for
and the retail market where it is usually judged by the total solids of cream itilk.
contains, which in turn dependspoint fat is by far the mostamount of fat.important
constituent of milk. Great quantities of milk are bought and sold at prices
depending solely upon' the test," or the amount of fat. This is a fair
arrangement so long as the milk is of good sanitary quality. It is obvious
that the value of milk for butter-making depends upon its fat content
because fat is the chief constituent of butter and the amount of butter
that can be made from a given quantity of milk is in proportion to the
amount of fat in the milk. The value of milk for cheese-making is also
indicated by its fat content. And the same is true in regard to milk for
the retail market, where it is usually judged by the quantity of cream it
contains, which in turn depends upon the amount of fat.

The New York law, which is rigidly enforced, states that milk must
contain at least 3 per cent fat but this same law also requires 12 per cent
of total solids, which is equivalent to requiring 3.25 per cent fat, since
at least that much fat is present in normal milk having 12 per cent solids.
The United States Government standard for pure milk calls for at least
3.25 per cent fat.
Average milk contains about 4 per cent of fat, but the amount in
milks from different herds varies from about 2.8 per cent to 6 per cent,
and still wider variations are found between milks from individual cows.
Even in the milk of a single cow there is a variation in fat from one
milking to another and it may amount to as much as or more than I per
cent; that is, a cow giving 3.5 per cent milk in the morning may give
4.5 per cent milk in the evening.
Every dairyman knows that the percentage of fat in the milk of his
different cows or the mixed milk of his herd varies from day to day and
month to month. The mixed milk varies less than the milk from a single
cow because all the cows of a herd do not vary in the same way or to the
same extent at the same time. Few things cause more discomfort to
some patrons of creameries, cheese factories and shipping stations than
the variations of their tests. Slight variations should be expected and
sometimes it is impossible to explain them. If the accuracy of the factory
test is suspected it is a simple matter to sample the milk at home and
test it with a hand tester that can be bought for a few dollars-less than
some patrons claim to be cheated in a single month. Often the feed of
the cows is held responsible for the test but it is wrong to think that feed
has any marked effect upon the percentage of fat in milk. This statement
does not agree with the belief of many experienced dairymen but it is
based upon a large number of carefully conducted feeding tests which
have shown that feeding effects the quantity of milk but not the quality
when the herd is in normal condition and has not been underfed. If cows
have been half starved, an abundant supply of good feed will greatly
increase the milk flow and it may very slightly increase the percentage of
fat. A sudden change of feed, however, may be the cause of temporarily
changing the fat content. Cows going dry or coming fresh may have
a noticeable effect upon the herd test as the milk becomes gradually richer
toward the close of the period of lactation. Sometimes this and other
equally obvious influences are overlooked by dairymen who do not under-
stand the variations of their tests. The climate and any condition affect-
ing the comfort of the cow or exciting her may have a marked influence




FAT- 2.5 GAR


FAT *.1

W AATER-90.5


WATER -90 .A


WATER 93.2

FIG. 220. Chart illustrating the composition of milk, cream, skilleted milk,
buttermilk and whey. Each rectangle represents zoo pounds, and the
different subdivisions show, the quantities of the different constituents.

upon the percentage of fat in milk. The period of heat or a slight indis-
position also has its effect. Even a change of milkers, if the cow is
accustomed to being milked by a certain person, or a more rapid milking
than usual may cause a change in the fat yield. It is a strange thing
that the same influences may not affect two cows alike. It is well known
that the richness of milk depends largely upon the breed of the cows.
In Milk and Its Products," Wing reports the average fat content of
milks of several dairy breeds as follows:
Jersey ........................................... 5.35
Guernsey ........................................ 5.16
Devon ............ ....... .............. ........... 4.60
Shorthorn ....................................... 4.05
Ayrshire ............ ........................... 3.66
Holstein-Friesian ................................. 3.42

Milk fat is made up by the combination of a number of different
compounds known as glycerides of fatty acids. According to chemical
authority, glycerides of soluble or volatile fatty acids constitute about
fifteen per cent of the fat mixture, and it is this large proportion which
forms an important distinction between butter fat and other fats (as in
oleomargarine) that are sometimes substituted for butter. The volatile
fats contribute to the flavor of butter.
As was stated above, fat is present in milk in the form of small globules.
The number of these is almost uncomprehensible. It is estimated that
there are about one hundred millions in one drop of milk-more than the
number of people in the United States. Many of the globules are so
small that it would take over ten thousand of them side by side to extend
one inch. Some of them float about in the milk serum independently, but
there is a tendency for the globules to form loose and irregularly shaped
clusters. Being lighter than the serum, they are always trying to rise
to the surface, but they are retarded by the viscosity or stickiness of the
fluid surrounding them. It is interesting to note that the fat globules of
Jersey and Guernsey milk average larger than those of other breeds. This
furnishes an explanation of the well-known fact that cream rises more
readily on Jersey and Guernsey milk than any other.
Casein.-This part of milk is commonly called the curd. It is a nitroge-
nous or albumenoid constituent. The average quantity of casein in milk
is about 2.6 per cent, but it varies more or less. It is not in perfect solu-
tion, as is the sugar, nor is it floating about in the form of small bodies,

as does the fat, but it may be said to be in partial solution somewhat in
the condition of a jelly. When milk becomes sour or when acid or rennet
is added to it the casein coagulates, forming curd or clabber, which is
one of the chief constituents of cheese. Casein possesses high food value,
and it is largely this that gives skimmed milk and buttermilk their value
as human or animal foods.
Albumen.-This is another nitrogenous constituent of milk, and it is
very similar to the white of egg. Only about .7 per cent of albumen is
present in milk and it is in solution. It may be coagulated or precipi-
tated by heat, 170' F. being high enough. This constituent also goes
into the skimmed milk or whey and increases its food value.
There are some other nitrogenous constituents of milk present in very
small quantity and not much is known about them. For practical pur-
poses they may be considered the same as casein or albumen.
Sugar.-Cow's milk contains more sugar than fat, the average amount
being about 5 per cent. The sugar is in solution in the water of the milk.
Its quantity fluctuates somewhat, but not as much as the quantity of fat,
and it gradually decreases when milk sours because the souring is due
to the changing of sugar into lactic acid by bacteria. As much as one-
fifth of the sugar may be transformed in this way.
Milk sugar is known also as lactose. It is a carbohydrate, and its
chemical formula is C12H,220,. H20, which means that each molecule
is made of 12 atoms of carbon, 22 atoms of hydrogen, II atoms of oxygen
and I molecule of water (H20). It has a high food value and is sep-
arated from whey as a regular article of commerce, being used largely
in the manufacture of infants' foods. Druggists use it also for coating
pills and other purposes. When marketed it has the appearance of
powdered sugar, but it is less soluble and less sweet than any of the
ordinary table sugars.
Practically all the sugar of milk goes into the skimmed milk and
buttermilk of a creamery, and much of the feeding value of those
by-products is due to the sugar they contain. Practically all of the sugar
of milk goes into the whey of the cheese factory, furnishing most of the
feeding value of that by-product.
Ash.-This is the mineral part of the milk and is what remains after
the water has been evaporated off and the solid matter has been burned.
Its color is grayish white. Normal milk contains about .7 per cent ash.
and this is partly in solution and partly in suspension. Ash contains
mineral matter required in the formation of bones and is a very

important constituent in milk or skimmed milk used as a food for the
Water.-Water forms about 87 per cent, or seven-eighths, of normal
cow's milk. When compared with the amount of water and refuse of
some other foods this is seen to be not excessively large. For example.
some meats contain more than 50 per cent water, besides io per cent to
20 per cent refuse. The water and refuse of some food fish amounts to as
much as 87 per cent of the total weight. Oysters, solids," contain over
88 per cent water. The water and refuse of very many fruits and vege-
tables constitute more than 90 per cent of their total weight.

2. Colostrum.
The secretion of the udder before and immediately after the birth of a
calf is called colostrum or beastings. It contains an excessively large
amount of albumen and is quite yellow in color and thick, and more or
less viscous or sticky. It is provided by nature as the first food for the
young and it changes gradually to normal milk in the course of three to
five days. It should not be used in market milk nor for butter or cheese-
making. Its composition is as follows:

Fat .............................................. 3.6
Casein and albumen ....................... .......... 17.6
Sugar........... ................................. 2.8
Ash.... ......................................... 5
Water .......................................... 74.5

3. Cream.
Few foods vary so much in composition as does cream.-It is made of
the same constituents as are found in milk but in different proportions.
Fat is the most variable and most important ingredient. It was stated
that the fat globules of milk are always trying to rise to the surface.
The largest globules rise the most easily because their volume is greatest
in proportion to their surface which is exposed to the retarding influences.
Many of the smaller globules are never able to make their way to the
surface, and remain below in the serum or skimmed milk. As the count-
less fat globules press upward the upper layers of the milk constantly
become richer and the term cream is used. It may be removed
or skimmed off." If the fat globules are not crowded together closely
the cream will be thin, poor or light, and test perhaps 15 per cent fat.

But if the rising of the fat globules has been favored by certain condi-
tions they may be densely crowded together and the cream will then be
thick, rich or heavy and test perhaps 25 per cent fat. With the aid of a
centrifugal separator almost all of the fat globules in milk can be crowded
very closely together forming cream that will test above 50 per cent fat.
But the separator can be adjusted to skim a thinner cream, and this is
usually done because such rich creams are too thick for practical purposes.
Each globule of fat always seems to be surrounded by a thin film of serum
(water, sugar, etc.), which keeps it apart from other globules and these
films are broken only by the concussion of churning, which permits the fat
to unite in large masses.
Thus it is seen that cream is the same as milk except that the serum
contains a larger number of fat globules and the richness of the cream
depends upon how near together the fat globules are packed. The follow-
ing figures represent the approximate composition of two samples of
cream of different richness:

Composition of cream.
Fat... ..... ........ ......... ......... 56.3 22.5
Casein and albumen ....................... 1.6 3.8
Sugar................................... 2.3 4.2
Ash.. ......... ................... .44 .5
W ater ....................... ........... 39-4 69.o

100.0 I00.0

On account of the large amount of fat in cream, its specific gravity is
less than that of milk and may be less than that of water.

4. Skimmed milk.
Skimmed milk consists of the serum of milk with more or less fat
globules floating in it depending upon the efficiency of separation. Thus
it contains the same constituents as milk and they are about in the same
proportion except fat. When cream is separated from milk by the gravity
method a large number of the fat globules are usually left in the skimmed
milk and it may test one per cent fat or higher. But when the cream is
taken by a centrifugal separator, only a very small amount of fat remains;
frequently this is found to be just a trace." There is always some fat
left in the form of the smallest globules because no power has been found

that is great enough to remove every one of them. The approximate com-
position of two samples of skimmed milk is as follows:
Gravity Separator
Fat........................ ........ ..... .9 .
Casein and albumen ........................ 3.2 3.6
Sugar............. .. ...... ... ......... 4.7 5.
Ash ................ ................ .7 .8
W ater.................................. 90.5 90.5

I00.0 100.0

The specific gravity of skimmed milk is about 1.036.
The food value of skimmed milk is commonly underestimated.-Pound
for pound it will compare well with many of our standard foods and it
has a great advantage over them when cost is considered. It should be
remembered that skimmed milk contains practically as much as whole
milk of the valuable nitrogenous or flesh-forming constituents, casein and
albumen, besides the milk sugar and ash. From the nutriment standpoint
the loss of the fat is not so serious a matter as is generally supposed.

5. Buttermilk.
This is the by-product remaining when butter is churned from cream.
In composition it is about the same as skimmed milk with a little more fat.
But in character and taste it is quite different, owing to the fact that cream
is usually allowed to sour before churning and the casein has coagulated
and been finely broken up in the churn. Many persons are very fond of
buttermilk, and undoubtedly it has high food value. Its composition is
given as follows, though less fat is found when the churning is done
with thoroughness:

Fat ...................................... ....... .5
Casein and albumen.................................. 3.6
Sugar (and lactic acid) ............................ 4.8
Ash............................................. .7
W ater ........................................... 90.4

6. Whey.
This is the by-product of cheese-making. Practically all of the fat and
casein of the milk, with a part of the water, go into the cheese. There
remains much water holding in solution sugar, albumen and ash and these
have considerable food value.

The composition of whey is about as follows:
Fat............................................... 3
Casein and albumen ................................ I.
Sugar... ............................. .......... 5.
Ash.............................................. .5
Water .......................................... 93.2

7. Other kinds of milk.
All female mammalia produce milk for their young and some have been
trained to produce it also for other purposes. In this country the cow is
the best known example of this latter class and the preceding pages refer
only to cow's milk. But in some parts of France and Italy and in other
countries the milk of the goat is an important kind. In Cuba ass'es
milk is considered a great delicacy for sick people, and it is reported that
in Spain sow's milk is used to some extent as a human food. The milks
of different 'kinds of mammalia are of the same general character but
differ more or less in the proportions of the various constituents.
According to Richmond the composition of milk of certain mammals is
as follows:
Composition of milks of different mammals.
Water Fat Casein Albumen Sugar Ash
percent percent percent percent percent percent
Cow ...... 87.10 3.90 3.00 .40 4.75 .75
Goat....... 86.04 4.63 3.49 .86 4.22 .76
Ewe ...... 79-46 8.63 5.23 1.45 4.28 .97
Woman.... 88.2 3.30 I.00 .50 6.80 .20

Mare...... 89.80 1.17 1.84 6.89 .30
Ass....... 90.12 1.26 1.32 -34 6.50 .46

Sow....... 84.04 4.55 7.23 3.13 1.05
Cat........ 81.63 3.33 3-12 5.96 4.91 -58

Elephant... 67.85 19.57 3.09 8.84 .65

These figures should not be taken too literally as one of the first things
to be learned by any one studying the composition of milk is that it varies
more or less under different conditions. Doubtless they represent reason-
ably fair averages but even this may not be the case with some of the
animals from which it would be very difficult to get samples for analysis.

8. The Babcock test.
There is one milk test that should be understood and used by every per-
son who has a dairy. It is the test for fat, and the method devised by Dr.
S. M. Babcock and bearing his name is the one in common use. When
properly made this test can be depended upon for accurate results, and
it is so simple and quick that any person can learn to make it. It is not
an exaggeration to say that the Babcock test already has been worth
millions of dollars to American dairy interests. On the farm it may be of
value to check the test made at the factory as was suggested above, but
its chief value there is to show the quality of milk given by the differ-

FIG. 222. The apparatus necessary for making the Babcock
test, which shows the percentage of fat in milk or cream.

ent cows. It is as important as scales for weighing milk. When used
with the scales it quickly shows which cows are unprofitable or failing to
pay for their board. It is not necessary to test every milking; a few
successive milkings may be tested and then no more tests be made for a
few weeks. This method will give results accurate enough for practical
The apparatus necessary for making the test consists of a centrifugal
machine, a few test bottles having long slender necks with a scale or
graduations marked upon them, a pipette or measure for the milk, an acid
measure and a bottle of sulphuric acid, all of which can be bought for
from about five to ten dollars depending upon the number of samples it
is wanted to whirl in the machine at one time. Briefly the method of
making the test is as follows: The milk to be tested is thoroughly mixed
and a small amount is put into the test bottle. It is necessary to have a

certain definite quantity (17.6 cubic centimeters, or a little more than half
an ounce) and the pipette is used for its measurement. A definite amount
of commercial sulphuric acid (with specific gravity of 1.82) is then
poured into the test bottle from the sulphuric acid measure and the milk
and acid are mixed. When a number of samples have been prepared they
are put into the machine to be whirled, care being taken to keep the
machine balanced by always putting one bottle opposite another. It is
necessary also to keep the samples warm throughout the test. Mixing the
acid with the milk produces considerable heat, but in cold weather hot
water should be put into the machine to keep it warm. The samples are
whirled for five minutes at the rate of about i,ooo times per minute. Then
the machine is stopped and enough hot water added to bring the contents
of each bottle up to the base of the neck. Again they are whirled for
about two minutes. Then the clear fat will be seen to be collected at the
base of the neck and hot water is added slowly until this fat has come up
into the neck where the scale will show its quantity. Whirl again for
one minute, then, while the fat is still hot, read the scale-marks at the
extreme upper and lower ends of the fat column. The differences between
these readings will be the percentage of fat in the milk. The fat column
should be clear and have the appearance of pure yellow oil. Expertness
with the test comes only with practice. More detailed instructions than
the above are usually furnished by the manufacturers of the machines and
are given in several dairy books and bulletins.
Other milk tests include the lactometer test for specific gravity which,
together with the fat test, shows fairly accurately the total solids of milk.
There are also tests for different adulterations or sophistication of milk,
such as the addition of coloring matter or preservatives, and there is a
test to determine whether or not milk has been heated to a high tempera-
ture. But none of these are important to the dairyman who produces milk
and has every facility to know whether or not it is pure.

9. Standardizing cream and milk.
When cream is being sent to the city trade or used for certain other
purposes it is often desired to have it contain a certain percentage of fat
and the same each day. It is difficult to adjust a separator to skim cream
always of the same richness and it has become a more or less common
practice to skim a heavy cream and standardize it. This is done by
mixing with it enough of the skimmed milk that has just been removed,
or whole milk or thinner cream, to reduce the fat content to the proper

The following is an easy and accurate way to determine the quantity
of skimmed milk, milk, or thin cream that must be added to a rich cream
to produce a cream of required richness or fat content:
Draw a rectangle and write at the two left-hand corners the percentages
of fat in the fluids to be mixed, and in the center, place the required per-
centage. At the upper right-hand corner put the number which represents
the difference between the two numbers standing in line with it, i. e., the
number in the center and the one at the lower left-hand corner. At the
lower right-hand corner put the number that represents the difference
between the two numbers in line with it. Now let the upper right-hand
number refer to the upper left and the lower right-hand to the lower left,
then the two right-hand numbers show the relative quantities of the fluids
represented at the left-hand corners that must be combined to give a fluid
of the desired standard which is represented in the center.
For example, suppose we have cream testing 39 per cent fat, and we
wish to standardize this to a 30-per-cent cream by the use of milk testing
5 per cent fat. Following the directions we have this diagram-
39 25


511 9

which shows at once that 39 per cent cream and_5 per cent-milk must be
combined in the proportion of 25 to 9 inv order to produce 30 per cent
cream. If we wish to use So pounds of 39 per cent cream, then 18 pounds
of 5 per cent milk must be added, as is shown by this proportion:
25 : 9 :: 50 : 18

Suppose we wish to find the proper amounts of the rich cream and
milk to produce 170 pounds of 30 per cent cream:
If we take 25 pounds of the 39 per cent cream and 9 pounds of the
5 per cent milk, as is the diagram, we will have a total of 34
pounds, but we want a total of 170 pounds, or five times as much; then
we must take five times as much of each of the ingredients, or 125 pounds
of 39 per cent cream and 45 pounds of the milk, as is shown by these
34 : 25 :: 170 : 125
34: 9:: 17o : 45

Milk dealers receiving their supply from many sources are learning the
importance of standardizing their milk so it will be even in quality from
day to day. Some of them pour all the milk received into one large vat
and thus get a fairly even mixture to be sent out on the different routes.
But they can use the above simple rule and obtain exact results. For
If it is wanted, to mix the milks from two dairies testing 4.9 per cent fat
and 3.5 per cent fat to produce a 4.6 per cent milk, the diagram shows
these milks must be mixed in the proportion of I.I to .3 or I to 3. Thus:

4.9 1.1


3.5 .3

If we have 120 pounds of the 4.9 p'r cent milk we must mix with it
32.7 pounds of 3.5 per cent milk, as is shown by this proportion:
II : 3 :: I20 : 32.7

Persons in towns and cities are beginning to learn that the commercial
value of milk depends upon its fat content and gradually they are becom-
ing willing to pay more for rich than for poor milk. This means that
it is in the interest of thcse who sell market milk to know just what they
are selling and to establish and maintain a standard for their product.
Some will sell milk testing 4 per cent fat, others will sell milk testing
perhaps 3.3 per cent fat, and others will make trade by adv-rtising and
supplying rich milk testing about 5 per cent fat. Already some milk
sellers guarantee their percentage of fat, and others will certainly do so
as the public comes to know what such guarantees mean. One of the
difficulties of this practice is that retail buyers cannot readily tell whether
they are receiving milk of the quality guaranteed, which becomes a matter
of much importance in some cases, such as in the artificial feeding of
infants. Recognizing this, the New York State Dairymen's Association,
at its last annual meeting, unanimously passed a resolution in favor of
a State law to make the use of a false guarantee as to fat content, punish-
able the same as when milk is adulterated and below the State standard.


1Reabing=ourse for farmers
S. W. FLETCHER, Supervisor.

SERIES V. ITHACA, N. Y., No. 22.

This Discussion-paper is sent out with all Farmers' Reading-Course
Bulletins, for two reasons. In the first place, we should like to know your
own ideas on these subjects. On some of these points you have probably
had experience which will be interesting and valuable to us. No matter
what the Bulletin says, if you have different ideas on any of these subjects,
do not hesitate to state them on this paper and give your reasons. We
can learn from each other.
In the second place, we should like to have you use this paper to ask
us questions. If there are any points which the Bulletin has not made
quite clear or if there are any problems in your farming, whether on these
subjects or any other farm subjects on which you think we may be able
to help you, write to us on this paper.
OF THE PREVIOUS BULLETIN (2C. postage). This paper will not be
returned to you, but we shall look it over as carefully as we would a
personal letter and write to you if there are any points about which
correspondence is desirable. You will please consider this Discussion-
paper, then, as a personal letter to us. It will be treated as such and
under no circumstances will your remarks be made public.
If you are not interested in this Reading-Course Bulletin, we have
others on other subjects, and we shall be glad to send any of these to you
on request. The titles of the five Series of the Reading-Course Bulletins
now available are: I. THE SOIL AND THE PLANT. 2. STOCK FEEDING.
3. ORCHARDING. 4. POULTRY. 5. DAIRYING. The Farmers Wives'
Reading-Course, on domestic subjects, is also sent to those who desire it.


For our own benefit we should be glad to have you answer (on these
sheets) any or all of the following questions, if you are interested in these
subjects, but we do not wish you to feel under any obligation to do this.

I. What is the amount of each of the different constituents in Too
pounds (or about 86 quarts) of skimmed milk?
2. Have you noticed any variation in the tests of your herd's milk?
State the causes so far as known.
3. What difficulties have you had with the Babcock test, if any? And
what remedies did you apply?
4. What is the effect of boiling on colostrum? Explain the change.
5. How much 25 per cent cream must be added to 70 pounds of 18
per cent cream to make it test 20 per cent?

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County ................... ---------- ----- Postoffice.... -----------.

Note.-Your name appears on our mailing list as this Bulletin is
addressed. If incorrect, please write us.
Address all correspondence to Farmers' Reading-Course, Ithaca, N. Y.