The first object is to secure a good quality of milk; then comes the consideration of how it shall be prepared: this must be in such manner as shall render it as nearly like human milk, in composition and digestibility, as possible.
Comparison of the tables just given shows that cow's milk contains more nitrogenous matter and salts, and less sugar, than human milk.[54] By diluting with water to reduce the protein and salts, and adding sugar and a little cream, the proportions of these different substances may be made to approximate those in mother's milk. In both the sugar is the same—lactose, or milk-sugar; the fats are also much alike in each; but the albuminous matter of cow's milk differs somewhat from that of human milk, particularly in the way in which it coagulates in the presence of acids. Human milk forms into small, light, feathery curds; cow's milk into large, compact, not so easily digested masses. It is necessary, therefore, to seek the means for preventing the coagulation of milk in large curds in the stomach of the child—in other words, to so treat cow's milk that it shall coagulate more like human milk. This may be done in two ways:
(1) By mixing into the milk some substance which shall separate the particles of albumen from each other, and so cause it to form into smaller masses.
(2) By partial predigestion.
To accomplish the first, it is necessary to use some diluting substance of a harmless nature; if it be nutritious, so much the better. For this, Mellin's food, barley-water, veal broth, lime-water, and gelatin are recommended.
Mellin's Food and other Attenuants
Mellin's food is a partially predigested grain, in such a condition that it can be assimilated by the infant; barley-water is valuable for its potash salts, in which cow's milk is deficient, and which the growing babe needs; veal broth is rich in lime; and lime-water neutralizes the acid of the gastric juice, so that milk is not acted upon so strongly, and consequently forms into a lighter curd.
Predigestion
The second method is that of partial predigestion, and is accomplished by the use of peptonizing agents, among which Fairchild's peptogenic milk-powder is good (directions for its use will be given later). On account of the expense of these preparations it is not probable that they will come into general use, except in cases of sickness.