144 ORIGIN OF THE BILE. 



the iiroblem to be solved, the question to be an- 

 swered, is matured and clearly put. Every exiDeri- 

 mental decision of any such question in the nega- 

 tive forms the starting-point of a new question, the 

 solution of which, when obtained, is the necessary 

 consequence of our having j^ut the first question. 



40. In the foregoing sections, no other consti- 

 tuent of the bile, besides choleic acid, has been 

 brought into the calculation ; i3ecause it alone is 

 known with certainty to contain nitrogen. Now, if 

 it be admitted that its nitrogen is derived from the 

 metamorj^hosed tissues, it is not improbable that 

 the carbon, and other elements which it contains, 

 are derived from the same source. 



There cannot be the smallest doubt, that in the 

 carnivora, the constituents of the urine and the bile 

 are derived from the transformation of comj^ounds 

 of proteine ; for, except fat, they consume no food 

 but such as contains proteine, or has been formed 

 from that substance. Their food is identical Avith 

 their blood ; and it is a matter of indifference which 

 of the two we select as the starting-point of the 

 chemical developement of the vital metamorphoses. 



There can be no greater contradiction, with re- 

 gard to the nutritive process, than to suppose that 

 the nitrogen of the food can pass into the urine as 

 urea, without having previously become part of an 

 organized tissue ; for albumen, the only constituent 

 of blood, which, from its amount, ought to be taken 

 into consideration, suffers not the slightest change 



