ted to 155 deg. or 170 deg. F. for
thirty minutes. A temperature of 155 deg. 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 deg. F. for an hour will keep
upon ice for two or three weeks; that heated to 155 deg. 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 deg. F. for an hour?_

There is abundant evidence that milk is rendered less digestible by
such heating; also that it is more constipating, and that for some
children its nutritive properties are interfered with, so that it may
cause scurvy; this, however, is not seen unless it is continued as the
sole food for a long period. These objections are of so much
importance that this plan of heating milk is not to be recommended for
general use.

_When is it advantageous to heat milk to 212 deg. F.?_

For use upon long journeys, such as crossing the ocean. Milk should
then be heated for one hour upon two successive days, without removing
the cotton stoppers from the bottles.

_Is milk in any way injured by heating to 155 deg. F. for thirty minutes?_

This point is not yet definitely settled. Such heating does not affect
the taste of milk and does not render it more constipating. The
unfavourable effects; if there are any, are so slight that they need
not deter one from the use of pasteurized milk, even for long periods.
The preference, however, should always be given to milk which is so
clean and so fresh as not to require any heating.

_How should milk be pasteurized?_

A convenient form of apparatus is that known as Freeman's
pasteurizer[5]; another is the Walker-Gordon pasteurizer.[6]

[5] This can be obtained at 411 West Fifty-ninth Street, New
York, with b