40. To sterilize milk, place the sealed bottles on a wire rack or a
perforated pie tin in a deep vessel, as for the pasteurizing of milk,
and pour cold water into the vessel until it nearly covers the bottles.
Then raise the temperature of the water quickly to the boiling point,
and after it has begun to bubble, allow it to boil for three quarters of
an hour. At the end of this time, cool the milk rapidly and then keep it
cool until it is used.

41. Although milk thus treated becomes safe, sterilization changes its
flavor and digestibility. If milk of this kind must be used, some raw
food should be given with it. A diet composed entirely of cooked food is
not so ideal as one in which some raw food is included, because raw
foods contain substances that are essential to health. The change that
takes place in the composition of milk that has been sterilized can be
easily observed. Such milk on becoming sour does not coagulate as does
pasteurized or raw milk, owing to the fact that the lime salts in the
milk are so changed by the high temperature as to prevent the thickening
process from taking place. Then, too, sterilized milk is not likely to
become sour even after considerable time. Still, such milk is not safe
to use except when it is fresh, for instead of fermenting in the usual
way it putrefies and is liable to cause such a dangerous sickness as
ptomaine poisoning.

42. MODIFIED MILK.--For infants who cannot be fed their normal diet,
cow's milk must be used as a substitute, but in order to make it a more
nearly ideal food for them it must usually be modified, or changed, by
adding other materials. When it is so treated, it is known as modified
milk. The materials used to modify milk are sterile water, lime water,
barley water, cream, skim milk, milk sugar, or some other easily
digested carbohydrate, one of these or a combination of them always