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A noticeable fact in this table is that skimmed milk differs from
unskimmed mainly in the withdrawal of the fat. Hence, if calves are fed
on skimmed milk, they should have in addition some food like corn meal
to take the place of the fat withdrawn. A calf cannot thrive on skimmed
milk alone. The amount of nourishing fat that a calf gets out of enough
milk to make a pound of butter can be bought, in the form of linseed or
corn meal, for a very small amount, while the butter-fat costs, for
table use, a much larger sum. Of course, then, it is not economical to
allow calves to use unskimmed milk. Some people undervalue skimmed milk;
with the addition of some fatty food it makes an excellent ration for
calves, pigs, and fowls.

Along with its dry matter, its protein, its carbohydrates, and its fats,
milk and its products possess another most important property. This
property is hard to describe, for its elements and its powers are not
yet fully understood. We do, however, know certainly this much: milk and
the foods made from it have power to promote health and favor growth in
a more marked degree than any other foods. It is generally agreed that
this is due to the health-promoting and health-preserving substances
which are called vitamines. Men of science are working with much care to
try to add to our knowledge of these vitamines, which have so marvelous
an influence on the health of all animals. Unless food, no matter how
good otherwise, contains these vitamines, it does not nourish the body
nor preserve bodily health as it should. A complete lack of vitamines in
our food would cause death. Since, then, milk and its products--butter,
cheese, curds--are rich in vitamines, these health-giving and
health-preserving foods should form a regular part of each person's
diet.

[Illustration: FIG. 270. AIRING THE CANS]

=Cream.= Cream is simply a mixture of butter-fat and milk. The
butter-fat floats in the milk in little globe-shaped bodies, or
globules. Since these globules are lighter than milk, they rise to the
surface. Skimming the milk is a mere gathering together of these
butter-fat globules. As most of the butter-fat is contained in the
cream, pains should be taken to get all the cream from the milk at
skimming time.

After the cream has been collected, it must be allowed to "ripen" or to
"sour" in order that it may be more easily churned. Churning is only a
second step to collect in a compact s