2. Modification Of The Percentage Composition Of Milk

The usual and most satisfactory method of carrying out this modification is to dilute milk with water, and add cream and sugar. By this means the protein percentage is reduced, while the fat and carbohydrate content is retained. It is unwise to give an infant, for any length of time, a mixture weaker than one part of milk and two parts of water. With such dilution the protein percentage is largely reduced, yet the initial relative preponderance of caseinogen in the protein was such that it is still present in larger quantities than in human milk.

Other diluents frequently employed are lime-water and barley-water. Lime-water, besides acting as a diluent, alters to a slight extent the proportion of lime salts present in the mixture, and also serves to render the mixture more alkaline. This last action is the most important, because rennin only acts in the presence of an acid, and consequently its action is delayed, and a less dense curd is formed in the stomach.

Barley-water contains minute amounts of protein, fat, and mineral salts, and a more considerable, though still small, amount of starch. It consequently possesses a small nutritive value, the most of which, however, is due to its starch content. The power of the infant to digest starch is comparatively weak, though it varies considerably in different children. It is, consequently, always advisable to know the strength of the barley-water which is being employed, and a useful method for its preparation is to add I tablespoonful of prepared barley flour to I pint of water, boil for twenty minutes, and make up with water again to a pint. The barley-water so prepared contains rather less than 1 per cent, of starch.

Milk may also be modified by separating it into its constituents - whey, cream, lactose, and water - and subsequently mixing them again, with or without the addition of fresh milk. Such a method of procedure is termed "the percentage method," and for its satisfactory conduct requires knowledge of the original richness of the milk. Lacking such knowledge, accurate percentage modifications are impossible, but the principle underlying the procedure is that which must guide us in our prescription of all milk-mixtures (see p. 242).

3. Alodifications To Increase Or Favour The Digestibility Of Milk

By the addition of sodium citrate to milk, many of the soluble calcium salts are precipitated, and as a result a smaller and softer rennin curd is formed in the stomach. One grain of sodium citrate added to 1 ounce of pure milk, or to so much of a milk mixture as contains 1 ounce of milk, serves partially to prevent rennin action, while 2 grains prevents it entirely.

By means of "peptonising powders," consisting of pancreatic extract and bicarbonate of soda, artificial .predigestion of milk can be obtained, more or less complete, according to the length of time which the powders are allowed to act.

The method of employment is simple, and consists in mixing the powder with the milk, and placing the bottle containing the mixture in water at a temperature of 110° F. for the length of time desired. Thus, after twenty minutes' heating, partial digestion occurs, and there is no bitter taste in the milk; while the longer it is heated - up to two hours - the more complete is the digestive process, and the more marked becomes the development of a bitter taste.

Various other preparations of milk as well as a variety of foods, are frequently used in the feeding of young children.

Buttermilk has practically the same protein and inorganic salt content as the ordinary milk: it contains, however, extremely little fat, and a diminished amount of sugar, as some of the sugar has been changed into lactic acid. Its two chief characteristics are, consequently, a small amount of fat and a large amount of lactic acid. This milk is very digestible, and may be given to the infant in the raw condition, whereby the benefit due to the presence of living lactic acid bacilli will be obtained. It is also frequently given mixed with flour and sugar and then boiled, and in such a case the characteristics of the food are its poverty in fat, its acidity, and its high carbohydrate content.

Infant Feeding

Condensed milk is cow's milk from which, as a rule, about two-thirds of the water has been removed by heating and evaporation; but as the composition of the original cow's milk is very variable, the composition of different brands of condensed milk is also variable. In addition to condensation of the milk, there is frequently also the addition to it of cane sugar, and we meet, therefore, with three types of condensed milk: -

1. Condensed whole milk, unsweetened.

2. Condensed whole milk, sweetened.

3. Condensed skimmed milk, sweetened.

It is obvious that for the use of the infant all types require plentiful dilution. Twofold dilution with water restores the original composition of the milk, with or without, according to the type, the addition of cane sugar. Further dilution, to make the amount of protein approximately correspond to that in mother's milk, results in the amount of fat being reduced to a minimum. The vast majority of all condensed milks are artificially sweetened with cane sugar, and their two outstanding characteristics are, accordingly, lack of fat and abundance of sugar (see p. 157).

Of such milks, two of the best are Nestle's and Milkmaid. What is their place in the feeding of the infant? In ordinary circumstances these milks are altogether undesirable as part of the diet of a healthy infant. When freely diluted and mixed with cream, the sugar and fat content of the mixture may be rendered satisfactory, but in such a case the protein content is utterly insufficient. If, on the other hand, the amount of protein present is to be satisfactory the quantity of carbohydrate is necessarily excessive. In extraordinary circumstances, however, they have a definite value, and for short periods form a safe and satisfactory diet. For sea-voyages and railway travelling, when milk from a Walker-Gordon dairy1 is not readily obtainable, they are excellent forms of nourishment, as are also the Allenbury foods, and in certain conditions of delicacy and disease in infancy to be mentioned later, their employment is of great value.

1 From such dairies sterilised milk can be obtained, modified according to prescription.