166 ORGANIC REMEDIAL AGENTS. 



nothing is left but to conclude that their elements take 

 a share in the formation of certain constituents of the 

 living body, or in the production of certain secretions. 



80. The vital process of secretion, in so far as it is 

 related to the chemical forces, has been subjected to 

 examination in the preceding pages. In the carnivora 

 we have reason to believe, that, without the addition of 

 any foreign matter in the food, the bile and the constit- 

 uents of the urine are formed in those parts where the 

 change of matter takes place. In other classes of ani- 

 mals, on the other hand, we may suppose that in the 

 organ of secretion itself, the secreted fluid is produced 

 from certain matters conveyed to it ; in the herbivora, 

 for example, the bile is formed from the elements of 

 starch along with those of a nitrogenized product of the 

 metamorphosis of the tissues. But this supposition by 

 no means excludes the opinion, that in the carnivora the 

 products of the metamorphosed tissues are resolved into 

 bile, uric acid, or urea, only after reaching the secreting 

 organ ; nor the opinion, that the elements of the non- 

 azotized food, conveyed, directly by the circulation to 

 every part of the body, where change of matter is going 

 on, may there unite with the elements of the metamor- 

 phosed tissues, to form the constituents of the bile and 

 of the urine. 



81. If we now assume, that certain medicinal agents 

 may become constituents of secretions, this can only 

 occur in two ways. Either they enter the circulation, 

 and take a direct share in the change of matter, in so 

 far as their elements enter into the composition of the 



