PRESERVATION OF MILK AND ITS TREATMENT 99 



of iron in the liver, but when, after six to nine months, this has 

 been used up, food containing iron must be given. Spinach and 

 egg-yolk (beaten up in thin semolina gruel or buttermilk soup) are 

 the best media for introducing iron, and the large lecithin content 

 of egg-yolk no doubt also contributes to the growth and welfare 

 of the child, lecithin being an important constituent of nerve and 

 brain. 



come into contact. Normal human milk contains twice to three times as 

 much iron as is present in cow's milk. On centrifuging, most of the natural 

 iron, as well as of the lecithin the latter is probably combined with the 

 proteins passes into the cream. Again, on churning, the bulk of these 

 constituents remains in the buttermilk, so that clear filtered butter fat is 

 free from lecithin. It will be seen from this that buttermilk, besides being 

 richer in fat than separated milk, is also richer in lecithin and organically 

 combined iron, both substances of very great physiological importance ; it 

 follows that separated milk in which fat has been emulsified cannot replace 

 unseparated milk. If it is found that buttermilk is more easily digested 

 than ordinary milk, the reason is that its casein is already so finely divided 

 that it can no longer form large lumps in the stomach. 



