54 NUTRITION OF CARNIVORA. 



The only excrement, strictly speaking, is a sub- 

 stance expelled by the urinary passage. When dry, 

 it is pure white, like chalk ; it contains much nitro- 

 gen, and a small quantity of carbonate and plios- 

 })hate of lime mixed with the mass. 



This excrement is urate of ammonia, a chemical 

 compound, in which the nitrogen bears to the carbon 

 the same proportion as in bicarbonate of ammonia. 

 For every equivalent of nitrogen it contains two 

 equivalents of carbon. 



But muscular fibre, blood, membranes, and skin, 

 contain four times as much carbon for the same 

 amount of nitrogen, or eight equivalents to one ; and 

 if we add to this the carbon of the fat and nervous 

 substance, it is obvious that the serpent has con- 

 sumed, for every equivalent of nitrogen, much more 

 than eight equivalents of carbon. 



If now we assume that the urate of ammonia con- 

 tains all the nitrogen of the animal consumed, then 

 at least six equivalents of carbon, which were in 

 combination with this nitrogen, must have been 

 given out in a different form from the two equiva- 

 lents which are found in the urate of ammonia. 



Now^ we know% with perfect certainty, that this 

 carbon has been given out through the skin and 

 lungs, w hich could only take place in the form of an 

 oxidised product. 



The excrements of a buzzard which had been fed 

 with beef, when taken out of the rectum, consisted, 

 accordinix to L. Gmelin and Tiedemann, of urate of 



