ACTION PATTERNS 299 



brain is the seat of a continual flow of opposing, assist- 

 ing, crossing and interfering impulses, the amount of 

 fatigue produced being proportional to the number 

 and strength of stimuli that evoke responses, whether 

 these responses be those of gross activity or of mere 

 perception. 



It is not \is difficult as it seems at first to conceive 

 how the most complex reactions have been built out 



FIG. 77. CROSS-SECTION OF LEAF AND HAIR OF VENUS' FLY-TRAP. 



Drawing showing the cellular mechanism which corresponds to the nerve 

 path in animals. The expansion or compression of these cells, resulting 

 from the touch of an insect, causes the leaf to close upon the insect in a few 

 seconds, like a trap. 



of the less complex by the simple process of multiply- 

 ing the number and sources of stimuli. In the motor 

 response of Venus' fly-trap we have a simple action 



