52 ANIMAL AND VEGETABLE 



of caseine, which is distinguished from fibrine and 

 albumen by its great solubility, and by not coagu- 

 lating when heated, the chief constituent of the mo- 

 ther's blood. To convert caseine into blood no fo- 

 reign substance is required, and in the conversion 

 of the mother's blood into caseine, no elements of 

 the constituents of the blood have been separated. 

 When chemicallv examined, caseine is found to 

 contain a much larger proportion of the earth of 

 bones than blood does, and that in a very soluble 

 form, capable of reaching every part of the body. 

 Thus, even in the earliest period of its life, the de- 

 velo]3ement of the organs, in which vitality resides, 

 is, in the carnivorous animal, dependant on the sup- 

 ply of a substance, identical in organic composition 

 with the chief constituents of its blood. 



What, then, is the use of the butter and the su- 

 gar of milk ? How does it happen that these sub- 

 stances are indispensable to life ? 



Butter and sugar of milk contain no fixed bases, 

 no soda or potash. Sugar of milk has a composition 

 closely allied to that of the other kinds of sugar, of 

 starch, and of gum ; all of them contain carbon and 

 the elements of water, the latter precisely in tlie 

 proportion to form water. 



There is added, therefore, by means of these com- 

 pounds, to the nitrogenised constituents of food, a 

 certain amount of carbon, or, as in the case of but- 

 ter, of carbon and hydrogen ; that is, an excess of 

 elements, which cannot possibly be employed in the 



