66 PHYSICAL CHEMISTRY IN MEDICINE. 



with a heterodrome reaction is indicated by the fact that 

 none of the substances which are formed in the destruc- 

 tion of the uric acid can be built up into the original 

 uric acid. 



It would lead us too far afield to discuss further the 

 fate of the different substances that enter into the metab- 

 olism of the organism in the light of our conception of 

 antagonistic reactions which can be combined among 

 themselves in the greatest variety of ways. In the last 

 analysis, no doubt, it is because the reaction is a hetero- 

 drome one that no path exists in the animal body over 

 which urea can again be built up into protein. 



The two components of an antagonistic reaction are 

 dependent upon each other only in so far as the one 

 furnishes the material necessary for the other. We can 

 easily see how in the fact that they can follow different 

 courses there resides the possibility that they can take 

 place simultaneously and side by side. This explains 

 also why ferments acting in opposite directions can 

 exhibit their characteristic effects without the presence 

 of separating walls in molecular proximity to each 

 other, as it were. 



Such reactions can without mutual interference take place 

 side by side, just as sound, light, and electric waves, or 

 currents of heat, electricity, and diffusion, can pass through 

 a medium simultaneously. 



V. 



The idea of homodrome and heterodrome antagonistic 

 reactions, as deduced from a consideration of changes 

 in the colloidal state and in metabolism, is closely related 



