THE URINE OF CARNIVORA. 79 



are separated from it in its passage through the 

 kidneys. 



The urine of the graminivora is alkaline ; it con- 

 tains alkaline carbonates in abundance, and so small 

 a portion of alkaline phosphates as to have been 

 overlooked by most observers. 



The deficiency or absence of alkaline phosj)hates 

 in 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 nitro- 

 gen in his daily food (about 4^ oz.), and that the 

 quantity of tissue metamorphosed 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 lbs. accord- 

 ing 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 produced in the foiTa of soluble alkaline 

 phosphates, must re-enter the circulation in this class 

 of animals. It is there employed in forming brain 

 and nervous matter, to which it is essential, and also, 

 no doubt, in contributing to the supply of the earthy 

 part of the bones. It is probable, however, that 



