warm place one or two days becomes sour. It
is then sometimes put into a tight box or barrel and beat in such a
way as to break up the little balls of fat. These are then pressed
together into a mass called _butter_. It requires a whole gallon of
milk to make one teacupful of butter. The milk remaining after the
butter is taken out is called _buttermilk_. Cheese is made from milk.

[Illustration: FIG. 20.--Two kinds of milk, showing the amount of fat
in each.]

=Milk as a Food.=--Milk is a healthful drink for nearly every one and
especially useful for those with weak bodies. During sickness it is
sometimes the only food the patient can take. It is well for children
to use two or three glasses of milk daily with their meals. It should
be sipped slowly so it will mix with the fluid in the mouth and not
form lumps called curds in the stomach.

A quart of milk contains more food for the body than a half pound of
good beefsteak. A pint of milk will supply the body with about as much
food as a pint of oysters. A bowl of milk and a half loaf of bread is
a healthful supper for a boy or girl. Skim milk and buttermilk are
healthful drinks which furnish much food for building bone, blood, and
muscle.

[Illustration: FIG. 21.--Germs which grow in milk and make it sour.]

=When Milk is a Poison.=--In New York, Cincinnati, and Chicago it has
been noticed for many years that large numbers of babies become sick
in warm weather and many of them die. The doctors learned that most of
the babies taken sick were being fed on cows' milk because their own
mothers did not have enough for them. It was then found that the sick
babies had been using milk from dairies where the stables were dirty,
the cows soiled, and the hands of the milkers unclean. On this account
much dirt got into the milk.

Babies fed on clean milk from clean cows kept in clean stables
remained strong and well. By much study the doctors learned that
_dirty milk is poisonous milk_. The poison is made by the germs or
bacteria living by the millions in unclean stables and in milk buckets
not well washed in boiling water. Dirty milk becomes most poisonous in
hot weather because warmth makes the germs grow very fast and become
so numerous that millions are present in a teaspoonful of milk.

=Keeping Milk Clean.=--During one week of hot weather in Cincinnati,
over a hundred babies were poisoned with dirty milk. In the same week
twice this number were made sick by unclean