270. The Unlike Curdling Of The Two Milks

The practical bearing of all these facts on the feeding of children is apparent when we come to observe the unlike curdling of the two milks. When a baby rejects cow's milk from its stomach, it is easily seen that the curds that have formed are of some size and show more or less solidity, that is, they look decidedly cheesy. On the contrary, when the food is the mother's milk, the curds are not nearly as evident, and are much more light and flaky. The same difference is observed in the laboratory when acid is added to the two milks. That from the cow permits the prompt and complete separation of the casein by coagulation, which is not the case with woman's milk, the coagulation being quite different. The greater adaptability of mother's milk to infant feeding seems to be due to the difference in the proportion of the various compounds and to their unlike physical condition rather than to any inferiority of the casein, sugar, and fats of cow's milk in performing the functions of growth and maintenance when once digested. It appears to be a matter of ease of digestion, rather than nutritive function. One writer1 advances the view that the difference, as infant's food, between cow's milk and mother's milk is mostly due to the larger proportion and consequent irritating influence of mineral salts in the former rather than to the differences in kind and quantity of the proteins and fat, but the facts cited can hardly be ignored in favor of this theory. It is not strange that the milk of the human mother is better suited to her young than that of any other species, otherwise Nature would seem to be a bungler.

1 Loc. cit., p. 796.

271. The Humanizing Of Cow's Milk

There are many cases where it is out of the question for the mother to feed her child with her own milk. Unless a "wet nurse" can be substituted, resort must be had to some artificial food, the one most commonly used being cow's milk. We have seen that cow's milk differs from human milk in the following particulars:

1. A larger proportion of solids, especially when it is from either Jersey or Guernsey animals.

2. Twice as large an average proportion of protein, four-fifths of which is casein, whereas in human milk only two-fifths of the protein is casein, the soluble proteins like albumin being proportionately more in the human milk protein.

1 The Lancet, Jan. 8, 1910.

3. A much smaller proportion of milk sugar in the solids.

4. A different combination of fats, the mixture melting at a lower temperature in mother's milk.

When cow's milk is to be fed to the infant, it would seem wise to eliminate these differences as fully as possible, although a complete similarity to mother's milk can hardly be reached. If cow's milk is diluted with an equal volume of water, the proportion of casein in the mixture becomes approximately like that in human milk. But this gives a proportion of solids altogether too low for satisfactory results, and besides, the solids are too poor in sugar and fat. The sugar and fat not only aid in nourishing the child, but a greater proportion so divides the particles of casein that its coagulation approaches more nearly that of mother's milk. The desired result may be practically accomplished by a combination of cow's milk, cream, milk sugar and barley water, the latter adding more or less albumin and other soluble matter that still further modifies the coagulation.