THE URINE OF CARNFVORA. 77 



the urine of the graminivora, obviously indicates the 

 slowness with which the tissues in this class of animals 

 are metamorphosed ; for if we assume, that a horse 

 consumes a quantity of vegetable fibrine and albumen 

 corresponding to the amount of nitrogen in his daily 

 food (about 4| oz.), and that the quantity of tissue met- 

 amorphosed is equal to that newly formed, then the 

 quantity of phosphoric acid which on these suppositions 

 would exist in the urine is not so small as not to be easily 

 detected by analysis in the daily secretion of urine 

 (3 Ibs. according to Boussingault) ; for it would amount 

 to 0*8 per cent. But, as above stated, most observers 

 have been unable to detect phosphoric acid in the urine 

 of the horse. 



Hence it is obvious, that the phosphoric acid, which, 

 in consequence of the metamorphosis of tissues is pro- 

 duced in the form of soluble alkaline phosphates, must 

 reenter the circulation in this class of animals. It is 

 there employed in forming brain and nervous matter, to 

 which it is essential. 



In the graminivora, therefore, whose food contains so 

 small a proportion of phosphorus or of phosphates, the 

 organism collects all the soluble phosphates produced by 

 the metamorphosis of tissues and employs them for the 

 development of the bones and of the phosphorized con- 

 stituents of the brain. The organs of excretion do not 

 separate these salts from the blood ; and the excrements 

 of the graminivora contain only insoluble earthy phos- 

 phates. 



7* 



