being employed. The proportion of these ingredients to use varies with
the age of the child that is to be fed and must be constantly changed to
meet the child's requirements. In the production of modified milk, a
physician's prescription and directions should always be followed
closely. Only the best quality of milk should be used, and, in addition,
the greatest care should be taken to have all the bottles, utensils, and
materials used as clean and sterile as it is possible to make them. If
such conditions cannot be met, it is advisable to pasteurize the
modified-milk mixture after the materials have been put together.


PRESERVED MILK

43. Besides milk that is commonly sold by dairymen and milk dealers, it
is possible to buy in the market many grades of so-called PRESERVED
MILK. Such milk is produced by driving off all or part of the water
contained in milk, and it is sold as _condensed, evaporated,_ and
_powdered milk_. Usually, it is put up in tin cans, and while it is not
used so extensively as regular milk, many firms are engaged in its
preparation.

44. CONDENSED AND EVAPORATED MILK.--As has just been mentioned,
condensed and evaporated milk is produced by the complete or partial
evaporation of the water contained in milk. Such milk can be shipped
long distances or kept for long periods of time, because it does not
contain sufficient moisture to permit the growth of bacteria. In
evaporating milk to produce these preserved milks, each gallon is
diminished in quantity to about two and one quarter pints, the original
87 per cent. of water being reduced to about 25 per cent. Therefore, in
order to use such milk, sufficient water must be added to restore it to