Yes; even when handled most carefully, milk contains many germs; but when carelessly handled, and in summer, the number is enormous. While most of these are harmless or cause only the souring of milk, others are occasionally present which may produce serious diseases such as typhoid fever, diphtheria scarlet fever, cholera, tuberculosis, and many forms of diarrhoea. _Under what circumstances is it necessary to sterilize milk?_ 1. In warm weather when it cannot be obtained fresh; hence always in cities and towns during the summer. 2. When one cannot be certain that the cows are healthy, or that the milk has been carefully handled. 3. When the milk is to be kept for any considerable time (i.e., over twenty-four hours), especially if no ice can be had. 4. During epidemics of typhoid fever, scarlet fever, diphtheria, or any form of diarrhoeal disease. _What are the two methods of heating milk?_ The first is known as _sterilizing_, in which the milk is heated to 212 deg. F. for one hour or one hour and a half; the second is known as _pasteurizing_, in which the milk is heated 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?_