Chemical Changes in Animal Organism. 309 



Results obtained by this method must be accepted 

 with some reserve, for it is possible that the administration 

 of substances in amounts larger than those which can be 

 completely metabolized may lead to a derangement of 

 certain functions of the organs, and the intermediary 

 products isolated may not be the normal ones. 



Another method for investigating the fate of inter- 

 mediary products is due to Knoop, who conceived the idea 

 of introducing into the substance under investigation a 

 resistant radicle which would therefore be excreted in 

 combination with some part of the original substance. 

 He studied the fate in the organism of certain fatty acids, 

 into which a phenyl group had been introduced, in a position 

 furthest removed from the carboxyl group. Some of his 

 chief results are summarized in the following table : 



