The tables given below are sufficiently accurate for home modification, provided the fat percentage of the whole milk is known.

From 4 Per Cent. Milk

To secure approximately a 10% fat, remove the upper 11 oz., or about one-third.

To secure approximately a 7% fat, remove the upper 16 oz., or about one-half.

From 525 to 5.50 per cent. (Jersey) Milk To secure approximately a 10% fat, remove the upper 15 oz., or nearly one-half.

To secure approximately a 7% fat, remove the upper 24 oz., or nearly three-fourths.

From 3.25 To 3.50 Per Cent. Milk

To secure approximately a 10% fat, remove the upper 8 oz., or about one-fourth.

To secure approximately a 7% fat, remove the upper 11 oz., or about one-third.

How To Obtain The Formulas Required For General Use

If one has at command three series or groups of formulas in which the fat has certain definite relations to the proteids, he will be equipped for the great majority of cases met with in practice. The three groups are as follows:

First Series, those in which the fat is three times the proteids.

Second Series, those in which the fat is twice the proteids.

Third Series, those in which the fat and proteids are nearly equal.

Fig. 1. The percentage of fat in different layers of milk.

Fig. 2. Chapin's dipper for removing the upper layers of milk.

Once thoroughly familiar with these groups of formulas, variations from them to suit the needs of the particular case can readily be made. In general, the First and Second Series, in which the fat is considerably higher than the pro-teids, are adapted to the early months, because at this period the infant as a rule has more difficulty in digesting proteids than in digesting fat. In the later months a higher proportion of proteids can be taken with the same percentage of fat. There are, however, other conditions besides age which must be taken into account, such as the vigor of constitution, the weight, and most of all, the peculiarities of the child's digestion. It is, therefore, impossible to say that at certain months certain proportions are desirable, and certain others at another period.

Formulas In Which The Fat Is Three Times The Proteids

This is nearly the relation which the fat and proteids bear to each other in a good sample of woman's milk. The easiest way to arrive at this would seem to be, first, to secure some milk or milk combination containing three times as much fat as proteids, and then dilute this according to the infant's age and digestion. After such dilution it will be necessary only to add the requisite amount of sugar and, when desired, lime water to complete the modification. This, in brief, is the whole process.

The most convenient combination for dilution is one containing 10 per cent. fat and 3.3 per cent. proteids. I shall call it a 10 per cent. milk, and refer to it subsequently as the primary formula of the First Series. The 10 per cent. milk may be obtained by removing the upper portion (see Fig. 1) from a quart bottle of milk, as described (p. 417, 418). This method will answer for persons who can obtain milk fresh from the cow, or for those who use bottled milk, provided the bottling is done at the dairy before the cream rises. The upper milk may be taken off with a siphon, spoon, or small dipper (Fig. 2); pouring off is not so accurate. For those who do not get their milk as above described, the additional fat can be secured by adding cream to the milk.

To secure a combination containing 10 per cent. fat, equal parts of plain milk and the ordinary (16 per cent.) cream should be used.

The next step is the manner and degree of dilution of the primary formula. It is convenient in our calculation to make up twenty ounces of the food at a time. For such a twenty-ounce mixture it is seldom necessary to use less than two ounces of our 10 per cent. milk. When one wishes to strengthen the food he gradually increases the amount of the 10 per cent. milk, one ounce at a time, making it successively three ounces, four ounces, five ounces, six ounces, etc., in a twenty-ounce mixture, the water, of course, being reduced by the same amount.

These mixtures may readily be translated into percentages by remembering that the percentage of fat is always exactly one-half the number of ounces of the 10 per cent. milk used in a twenty-ounce mixture. Thus, using three ounces will give 1.5 per cent. fat; four ounces, 2 per cent. fat; six ounces, 3 per cent. fat, etc. The proteids will continue to be in every instance exactly one-third the fat, as in the primary formula.

The amount of milk sugar needed to bring this up to the percentage usually required (5.5 to 6.5) is one ounce in each twenty-ounce mixture. One may obtain from a druggist a box holding exactly one ounce of sugar, or may measure in a tablespoon, calculating two and one-half even tablespoonfuls as one ounce. This sugar is dissolved in the water used for diluting the milk.

The usual proportion of limewater added is 5 per cent., or one ounce in a twenty-ounce mixture; this may be easily increased to any desired quantity. The foregoing directions may be expressed in the following table:

First Series of Formulas. Fat to proteids, 3:1. (See p. 421).

Primary Formula

10 per cent. milk - or fat 10 per cent., sugar 4.3 per cent, proteids 3.3 per cent. Obtained (1) as upper portion of bottled milk (p. 418), or (2) equal parts milk and (16 per cent.) cream.

Making more than a twenty-ounce mixture will be found very simple if we calculate for twenty-five, thirty, thirty-five ounces, etc. Thus for twenty-five ounces we add one-fourth more of each ingredient; for thirty ounces one-half more, etc. For twenty-five ounces of eleven, therefore, the exact formula would be: 10 per cent. milk, three and three-quarter ounces; milk sugar, one and one-quarter ounces; limewater, one and one-quarter ounces; water q. s. to make twenty-five ounces - i. e., twenty ounces.1