60 MAN AN ADAPTIVE MECHANISM 



poets have often compared it, to a splendid symphony 

 composed of notes to which the strings of the human 

 instrument have become attuned and to which they 

 respond when stimulated by the surrounding environ- 

 mental forces. 



The Principle of the Final Common Path 



According to Sherrington the organism of man is 

 integrated to respond as a whole to any adequate stim- 

 ulus, this integration being accomplished mainly by the 

 nervous system through the medium of the brain. The 

 brain responds to but one stimulus at a time, although 

 it acts with such rapidity and with such capacity for 

 kaleidoscopic changes that it seems to be performing 

 a number of acts simultaneously. That stimulus 

 which secures possession of the brain over all other 

 stimuli which are simultaneously striving for entrance 

 is said to possess the final common path an expres- 

 sion introduced by Sherrington. The final common 

 path is always the path of action. Could every ceptor 

 of the body be stimulated simultaneously, the brain, 

 hence the body, would respond to but one stimulus, 

 that being the one which has proven most important 

 to the survival of the race. Could every ceptor of the 

 body be equally and simultaneously stimulated, that 

 is, with the same (phylogenetic) force, there would 

 be no action. Could the pain ceptors of an animal be 

 equally and simultaneously stimulated, there would be 

 no pain. The attempt of the brain to discharge en- 

 ergy in response to one stimulus would be balanced by 

 the other stimuli and inaction would result, or even 

 death might occur. If the body were immersed in^ 



