DOMESTICATED ANIMALS. 81 



entertain a doubt that such food, in its various forms of 

 starch, sugar, &c., is closely connected with the pro- 

 duction of fat. 



In the natural course of scientific research, we draw 

 conclusions from the food in regard to the tissues or 

 substances formed from it ; from the nitrogenized con- 

 stituents of plants we draw certain inferences as to the 

 nitrogenized constituents of the blood ; and it is quite 

 in accordance with this, the natural method, that we 

 should seek to establish the relations of those parts of 

 our food which are devoid of nitrogen and those parts 

 of the body which contain none of that element. It is 

 impossible to overlook the very intimate connexion be- 

 tween them. 



If we compare the composition of sugar of milk, of 

 starch, and of the other varieties of sugar, with that of 

 mutton and beef suet, and of human fat, we find that in 

 all of them the proportion of carbon to hydrogen is the 

 same, and that they only differ in that of oxygen. 



According to the analyses of Chevreul, mutton fat, 

 human fat, and hog's lard contain 79 per cent, of carbon 

 to 11*1, 11*4, and 11*7 per cent, of hydrogen respec- 

 tively. (ie) 



Starch contains 44-91 carbon to 6-11 hydrogen. 

 Gum and sugar 42-58 to 6-57 ditto. (w) 



It is obvious that these numbers, representing the 

 relative proportions of carbon and hydrogen in starch, 

 gum, and sugar, are in the same ratio as the carbon and 

 hydrogen in the different kinds of fat ; for 



44-91 : 6-11 = 79 : 10-75 

 42-58 : 6-37 = 79 : 11-82 



