ACTION PATTERNS 305 



nerve impulse on reaching the brain may have access 

 to any one of the innumerable patterns, entrance is 

 secured to only that pattern by which the least re- 

 sistance is offered. That is to say, whether an im- 

 pulse shall pass over this or that or any action pattern 

 depends upon the degree of resistance which has been 

 established by the past experience of the organism ; 

 while the degree of vigor of the response depends upon 

 the physical state of the brain-cells. 



The assumption that by the lack of insulation each 

 pattern is connected with every part of the brain 

 with all the brain-cells suggests an explanation of 

 the fact that all the energy of the brain may be drawn 

 upon by any one or by a group of action patterns ; 

 thus, for example, the vigorous continuous use of the 

 muscles of a hand or a foot may ultimately exhaust 

 the entire brain. 



The postulation of receptor mechanisms effector 

 ceptors within the brain receives some support from 

 the following arguments : (a) In some fish receptor 

 mechanisms are known to exist in the brain ; (6) the 

 eye and other sense organs may be considered as re- 

 ceptor mechanisms projected outside of the brain ; 



(c) the known receptor mechanism of the eye bears a 

 resemblance to certain structures within the brain 

 whose function may equally well be receptive (Fig. 78) ; 



(d) if the nerve receptor mechanisms of the eye, the 

 ear and other sense organs are adapted to specific 

 energies, why may not similar nerve structures within 

 the brain likewise act as specific energy receptors? 



(e) if the sense receptor organs mediate between the 

 external environment and the brain, why is it not 



