required number of ounces are measured off. Skimmed milk is
estimated as being fat-free (although this is not entirely accurate).
Both gravity cream and skimmed milk are estimated as containing 3.2%
protein, and 4.5% sugar. In this method, one rounded tablespoonful of
milk sugar is estimated as weighing one half ounce (dextri-maltose may
be estimated in the same way). With this brief explanation of the
terms used we will proceed with the method itself.

It is always essential before beginning the calculation of the
formula, to know what percentages of fat, sugar, and protein it is to
contain, and the amount to be given in twenty-four hours; it is also
necessary to know how much lime water is to be added if this substance
is to form a part of the formula.

Suppose a thirty-two-ounce mixture is to be made containing 3% of fat,
6% of sugar, 2% of protein, and lime water sufficient to equal 25% of
the cream and skimmed milk in the mixture. The fat in the food must be
derived from cream, since it is the only substance containing fat to
be used in the formula. If the food was composed entirely of gravity
cream it would contain 16% of fat. Since it is to contain but 3% of
fat it is evident that only 3/16 of the mixture must be gravity cream,
3/16 of thirty-two ounces is six ounces. Six ounces of gravity cream
will, therefore, provide the 3% of fat desired in the mixture. The
gravity cream contains protein as well as fat. There are six ounces of
gravity cream in the thirty-two-ounce mixture. The protein content of
gravity cream is 3.2%. The protein content of a thirty-two-ounce
mixture containing six ounces of gravity cream is evidently 6/32 of
3.2% or 0.60%. Two per cent protein is, however, desired in the
mixture. The gravity cream has provided only 0.60%. One and forty
hundredths per cent of protein, the difference between the percentage
of protein desired and that furnished by the gravity cream, must be
obtained in some other way. It must be obtained, moreover, from some
substance which does not contain fat. Skimmed milk is such a
substance. Skimmed milk contains 3.2% protein. In order to get 1.40
per cent in the mixture by the use of skimmed milk, it is evident
that 140/320 of the mixture must be skimmed milk. 140/320 of
thirty-two ounces is fourteen ounces. Fourteen ounces of skimmed milk
will, therefore, provide the additional 1.40% of protein desired.

Both gravity cream and skimmed milk contain 4.50% milk sugar. Twen