1 68 MAN, THE ANIMAL 



the method accompanying the traveling of a stim- 

 ulus although no one had proved it. This discov- 

 ery was made by studying the transmission of a 

 stimulus along the dendritic portion of a sensory 

 nerve. Inasmuch as there does not appear to be 

 anything distinctive about such a stimulus, it is con- 

 cluded that all stimuli require the same conditions 

 and that carbon dioxide is formed each time a stim- 

 ulus passes along a nerve fiber. If this conclusion 

 is correct, then one must say that when several 

 nerve reactions are associated as in reflex action 

 that this likewise is a vital process. The carbon 

 dioxide formed in nervous activity is just like the 

 same process in muscles and in so far as exact 

 measurements are at hand, the general metabolism 

 of these highly specialized cells is identical with 

 what takes place in other parts of the body. 

 There is no justification in claiming that special 

 foods are required to make the nervous system go. 

 No new principles have ever been discovered by 

 scientists as they painstakingly applied the recent 

 findings in chemistry to this intricate problem. 



It remains to indicate briefly the nature of the 

 synapse deferring some of the implications grow- 

 ing out of the nature of the synapse for the fol- 

 lowing chapter. 



The discussion thus far has omitted all refer- 

 ence to one essential question, i.e., the passing of a 



