98 SECEETION. 



existence, the child derives all the inorganic, as well as the 

 organic matters necessary to nutrition and development, 

 from the breast of the mother. The reaction of the milk 

 depends upon the presence of the alkaline carbonates, and 

 these principles are important in preserving the fluidity of 

 the caseine. It is not determined precisely in what form 

 iron exists in the milk, but its presence here is undoubted. 

 A comparison of the composition of the milk with that 

 of the blood will show that most of the important in- 

 organic principles found in the latter fluid exist also in 

 the milk. 



Hoppe has indicated the presence of carbonic acid, nitro- 

 gen, and oxygen, in solution, in milk. 1 Of these gases, car- 

 bonic acid is the most abundant. It is well known that the 

 presence of gases in solution in liquids renders them more 

 agreeable to the taste, and carbonic acid increases very ma- 

 terially their solvent properties. Aside from these considera- 

 tions, the precise function of the gaseous constituents of the 

 milk is not apparent. 



A study of the composition of the milk fully confirms 

 the fact, which we have already had occasion to state, that 

 this is a typical alimentary fluid, and presents in itself the 

 proper proportion and variety of material for the nourish- 

 ment of the body during the period when the development 

 of the system is going on with its maximum of activity. 

 The form in which its different nutritive constituents exist 

 is such that they are easily digested and are assimilated 

 with great rapidity. 



Variations in the Composition of the Milk. 



The most elaborate researches concerning the variations 

 in the composition of the milk are those of Yernois and 

 Becquerel. Their observations relate to the composition 

 of milk both in health and disease ; but we shall consider 



1 Loc. dt. 



