_What are the two methods of heating milk?_

The first is known as _sterilizing_, in which the milk is heated to
212° F. for one hour or one hour and a half; the second is known as
_pasteurizing_, in which the milk is heated to 155° or 170° F. for
thirty minutes. A temperature of 155° F. continued for thirty minutes
is sufficient to kill the germs of the diseases above referred to.

_Will milk which has been thus treated keep indefinitely?_

No; for although all the living germs may be killed, there are many
undeveloped germs, or spores, which are not destroyed, and which soon
grow into living germs. Milk heated to 212° F. for an hour will keep
upon ice for two or three weeks; that heated to 155° F. for two or
three days.

_Is milk which has been sterilized always a safe food?_

No; for the reason that the milk may be so old, so dirty, and so
contaminated before sterilizing that it may be still unfit for food,
though it contains no living germs.

_Is cow's milk rendered more digestible by being heated in this way?_

Sterilizing milk does not improve its digestibility but rather the
contrary. Sterilized milk should be modified for infant feeding in the
same way as milk which has not been heated.

_Is milk in any way injured by heating to 212° F. for an hour?_