ANIMAL NUTRITION. 53 



tritive materials for their sustenance, and for the 

 exercise of their various and higher faculties. The 

 materials of animal nutrition must, in all cases, 

 have previously been combined in a peculiar mode ; 

 which combination the powers of organization alone 

 can effect. In the conversion of vegetable into 

 animal matter, the principal changes in chemical 

 composition which the former undergoes are, first, 

 the abstraction of a certain proportion of carbon ; 

 and, secondly, the addition of nitrogen.* Other 

 changes, however, less easily appreciable, though 

 perhaps as important as the former, take place to 

 a great extent with regard to the proportions of 

 saline, earthy, and metallic ingredients ; all of 

 which, and more especially iron, exist in greater 

 quantity in animal than in vegetable bodies. The 

 former also contain a larger proportion of sulphur 

 and phosphorus than the latter. 



The equitable mode in which nature dispenses 

 to her innumerable offspring the food she has pro- 

 vided for their subsistence, apportioning to each 

 the quantity and the kind most consonant to en- 

 larged views of prospective beneficence, is calcu- 

 lated to excite our highest wonder and admiration. 

 While the waste is the smallest possible, we find 



* The recent researches of Messrs. Macaire and Marcet tend to 

 establish the important fact, tliat both the chyle and the blood of 

 herbivorous and of carnivorous quadrupeds are identical iti their 

 chemical composition, in as far, at least, as concerns their ultimate 

 analysis. They found, in particular, the same proportion of nitrogen 

 in the chyle, whatever kind of food the animal habitually con- 

 sumed ; and it was also the same in the blood, whether of carni- 

 vorous or herbivorous animals ; although this last fluid contains 

 more nitro-en than the chyle. (Mcmoires de la Socictc dc Physiijne 

 ct d'Hisioire Naturelle de Geneve^ v. 389.) 



