milker's hands.

3. Require the milker to be clean in person and dress.

4. Milk quietly, quickly, thoroughly. Never leave a drop of milk in the
cow's udder.

5. Do not allow cats, dogs, or other animals around at milking-time.

_Utensils_

1. Use only tin or metal cans and pails.

2. See that all utensils are thoroughly clean and free from rust.

3. Require all cans and pails to be scalded immediately after they are
used.

4. After milking, keep the utensils inverted in pure air, and sun them,
if possible, until they are wanted for use.

5. Always sterilize the churn with steam or boiling water before and
after churning. This prevents any odors or bad flavors from affecting
the butter. All cans, pails, and bottles should also be sterilized
daily.

[Illustration]

SECTION LXII. HOW MILK SOURS

[Illustration: FIG. 273. MICROSCOPIC APPEARANCE OF PURE AND IMPURE MILK
At the left, pure milk; at the right, milk after standing in a warm room
for a few hours in a dirty dish, showing, besides the fat-globules, many
forms of bacteria]

On another page you have been told how the yeast plant grows in cider
and causes it to sour, and how bacteria sometimes cause disease in
animals and plants. Now you must learn what these same living forms have
to do with the souring of milk, and maybe you will not forget how you
can prevent your milk from souring. In the first place, milk sours
because bacteria from the air fall into the milk, begin to grow, and
very shortly change the sugar of the milk to an acid. When this acid
becomes abundant, the milk begins to curdle. As you know, the bacteria
are in air, in water, and in barn dust; they stick on bits of hay and
stick to the cow. They are most plentiful, however, in milk that has
soured; hence, if we pour a little sour milk into a pail of fresh milk,
the fresh milk will sour very quickly, because we have, so to speak,
"seeded" or "planted" the fresh milk with the souring germs. No one, of
course, ever does this purposely in the dairy, yet people sometimes do
what amounts to the same thing--that is, put fresh milk into poorly
cleaned pails or pans, the cracks and corners of which are cozy homes
for millions of germs left from the last sour milk contained in the
vessel. It follows, then, that all utensils used in the dairy should be
thoroughly scalded so as to kill all germs present, and particular care
should be taken to clean the cracks and crevices, for in them the germs