158 RELATION OF STARCH, &c. TO BILE. 



if added together, contain the elements of choleic 



acid; 



1 at. choloidic acid = C 73 H^O^ 



1 at. taurine = C 4 N H 7 O, 



1 at. ammonia ... = N H 3 



1 at. oholeic acid = 



if all this be considered, every doubt as to the pos- 

 sibility of these changes is removed. 



59. Chemical analysis and the study of the living 

 animal body mutually support each other; and 

 both lead to the conclusion that a certain portion 

 of the carbon of the non-azotised constituents of 

 food (of starch, &c., the elements of respiration) 

 is secreted by the liver in the form of bile ; and 

 further, that the nitrogenised products of the trans- 

 formation of tissues in the herbivora do not, as in 

 the carnivora, reach the kidneys immediately or 

 directly, but that, before their expulsion from the 

 body in the form of urine, they take a share in cer- 

 tain other processes, especially in the formation of 

 the bile. 



They are conveyed to the liver with the non- 

 azotised constituents of the food ; they are returned 

 to the circulation in the form of bile, and are not 

 expelled by the kidneys till they have thus served 

 for the production of the most important of the sub- 

 stances employed in respiration. 



60. When the urine is left to itself, the urea 

 which it contains is converted into carbonate of 

 ammonia ; the elements of urea are in such propor- 



