CHEMISTRY OF THE FEEDIXG OF ANIMALS. 195 



Were it not, then, that man separates the husk from the flour, 

 and that he gets lower animals to eliminate in an easily digestible 

 form a portion of his nitrogenous aliment, from foods which he 

 could not himself readily digest, and that he gets them also to 

 provide him with a portion of his respiratory and fat-storing food 

 in the concentrated form of fat itself, we could hardly account for 

 the less proportion to a given weight of the body of the stomach — 

 the receptacle and first laboratory of the food — in his case than 

 in that of the pig. We know, indeed, that in the cases where 

 man is reduced to depend for nearly the whole of the non-nitro- 

 genous constituents of his food upon starch, in the form of pota- 

 toes or rice, there is a disposition to an enlargement of the 

 abdominal organs, and to a diminution in physical and mental 

 energy. 



To conclude on this point, there can be no doubt whatever that 

 the food of the laboring man is improved when he can add to his 

 bread a portion of fat bacon, or butter, or fat in some other form, 

 and it is better still if he can substitute or supplement a little 

 butcher's meat. Indeed, that which common experience recog- 

 nises as high quality of diet is, within certain limits, high pro- 

 portion of animal to vegetable food, and with it J:ngh proportion 

 of fat to starch and other non-nitrogenous compounds. 



But not only do the animals which we fatten for our own food 

 convert vegetable produce which we either could not digest at all, 

 or could do much less easily than they, into concentrated and 

 easily' digestible and assimilable material for our use, but in doing 

 this they supply carbonic acid to the atmosphere, and return the 

 most impoi'tant manurial constituents of their food in their excre- 

 ments, thus providing, to both the soil and the atmosphere, from 

 crude vegetable products, that which is necessary for the luxuri- 

 ant growth of cereal grain, and other vegetable produce suited for 

 the direct use as food for man. 



Were it not for such compensations, by the increase of man and 

 other animals upon the surface of the earth (if it could take place 

 at all), by the enormous quantities of carbonic acid evolved into 

 the atmosphere from the combustion of coal and from other 

 sources, and by the gradual destruction of forests, which are the 

 chief natural agents for restoring the balance, the purity of the 

 atmosphere would become affected. But the grasses, which sup- 

 ply so large a proportion of the food of beasts, and the cereals 

 and the other plants of the same great family, which supply food 



