1242 



PHYSIOLOGY 



CHEMICAL CONSTITUTION OF DIFFERENT PROTEINS 



animal. Thus, in the calf the brain is only -^1^ of the whole animal. In 

 cow's milk lecithin is present in the proportion of 1 -4 per cent, of the total 

 protein. In the puppy the brain is ^ of the whole body and the proportion 

 of lecithin to protein in the milk is 2-11 per cent. In the infant, the brain 

 forms -^ of the body weight, while the lecithin is 3-05 per cent, of the protein 

 of human milk. 



We thus see that under normal conditions the young animal is supplied 

 through its natural food with all the food-stuffs in the proportions which it 

 requires for its normal nourishment and growth. It is impossible therefore 

 satisfactorily to replace the natural milk of an animal by that of another 

 species. In civilised communities it is becoming more and more the custom 

 to endeavour to feed the child with cow's milk, more or less modified, in the 

 vain endeavour to reproduce the properties of human milk. Among all 

 classes this involves the administering of a milk differing in its qualities 

 and in the relative proportions of its proteins, its fats, carbohydrates, and 

 salts, from human milk. So-called ' humanised ' milk is only a rough imita- 

 tion of the natural mother's milk. Among the poorer classes this artificial 

 feeding means the replacement of a natural sterile food, throwing very little 

 work on the digestive organs of the child, by a foreign milk, very difficult 



