No less important than the correct proportions of the ingredients, is freedom from disease germs and bacteria of putrefaction. Complete sterilization is possible by prolonged boiling; but experience has proved that under prolonged exposure to a temperature near the boiling-point certain changes take place in the albuminoids of the milk which greatly impair its digestibility. Full sterilization of milk for infant feeding has therefore practically been abandoned. It has been found that milk heated to 167∞ F. for twenty minutes, and promptly chilled by placing on ice, remains practically sterile for twenty-four hours, and it is spared the injurious changes which take place at a higher temperature. This process is known as Pasteurization. The Arnold steam sterilizer affords a convenient method of sterilizing; if used with the cover removed, the steam chamber being open, the temperature of the steam chamber does not exceed 170∞ F. It is claimed that in the Arnold steam sterilizer, with the use of a suitable gas stove, the water begins to boil at the end of two minutes after the gas is lighted. A four-ounce bottle of milk at an initial temperature of 70∞ F. in the open steam chamber attains a temperature of 170∞ in just one hour. An exposure of about one hour and twenty minutes in the steam chamber is therefore necessary for the Pasteurization. The rules for sterilizing are as follows: First, clean the bottles thoroughly; then place them in cold water, which is allowed to come to boil and boiled for ten minutes. Second, fill each with the milk you wish to use; put in the rubber cork without the glass plug; this leaves a small opening in the rubber cork; set the bottle in the basket, then in the boiler. Third, set in the refrigerator until needed for use. Fourth, when wanted for use, place a bottle of the milk so prepared in the tin mug which accompanies the sterilizer; fill the mug with hot water to the height of the milk in the bottle, heat the milk to the temperature of 99∞ F., remove the rubber cork and put on the nipple, when it is ready for use. Fifth, cleanse the bottle immediately after using; throw away any milk that has not been used. Sixth, if the steaming process is preferred, place the basket without the bottles in the boiler, fill the water up to, but not above, the bottom of the basket, place the bottles in the basket, and proceed as before. It is important that the milk should be sterilized or Pasteurized as soon as it is served in the morning. Each bottle must be thoroughly washed as soon as it is emptied. Milk sterilized in this way will keep for days without spoiling, as it is hermetically sealed and all the unhealthy germs have been removed. The most exact method for the artificial feeding of infants, and that which most nearly approaches the mother's milk, is that used by the "Walker-Gordon Laboratory," branches of which are to be found in many of the large cities.