INORGANIC FOODS. 



405 



One hundred parts by weight contain: (a) Before the animal has 

 doubled its weight at birth: 



(/>) After the animal has doubled its weight: 



During lactation the albumin content of milk diminishes gradually, 

 while substances such as sugar and fat, which are less essential as build- 

 ing material, but are rather to be regarded as sources of energy and heat, 

 tend to increase in amount. 



The remarkably small amount of phosphoric acid contained in human 

 milk is nevertheless sufficient for the development of the child, although 

 this takes place much more slowly than is the case with most mammals. 

 The above relations between the rate of growth and the composition of 

 the milk make it perfectly apparent how difficult it must be to replace one 

 kind of milk with that of another species. Evidently if the new milk 

 contains any constituent in amount less than the required minimum, 



