70 THE COMMON SENSE OF THE MILK QUESTION 



babies, it is necessary to pay attention to other factors 

 beside the percentages of protein, fat, and carbo- 

 hydrates which the substitute contains. Even if we 

 could secure a milk the chemical composition of which 

 was exactly the same as that of human milk, it would 

 still be far from a perfect substitute, imless it behaved 

 similarly in the digestive process. It is evident, then, 

 that while a chemical analysis is necessary and 

 helpful, it is not, by itself, competent to warrant the 

 fitness of the milk of any animal as a food for any other 

 than its own young. Comparative anatomy of the 

 digestive organs, and a close study of their function- 

 ing, must go hand in hand with chemical analysis.^ 



Furthermore, the chemical analysis of milk must be 

 carried much farther than is necessary to determine 

 the proportion of the various food constituents con- 

 tained in it. That is but the beginning of physio- 

 logical chemistry as it bears upon the problem of the 

 artificial feeding of infants. There are many other 

 matters of profound importance which need to be just 

 as carefully studied. For example, there is in all 

 milk fats a substance of a phosphorescent nature, 

 called lecithin — from the Greek root, lekithos, 

 yolk of an egg. This substance is contained in hu- 

 man milk to a much greater degree than in the milk 

 fat of other animals, such as the cow and the goat. 

 That there is a very good reason for this may be pre- 

 sumed, for Nature's economy is exceedingly scientific 



