ins THI: \KK\OIS SYSTKM AND ITS CO.\SKI;\ ATK>\ 



taking of an additional step to be added to the Lengthening 

 series. Visual impulses, varied with the changing scenery, 

 have been giving rise to cereliral currents which have 

 favored the holding of the muscles to their long task. But 

 now a time has come when the impulses returning from the 

 locomotor organs are deterrent rather than encouraging. 

 Inhibition at the lower centers is overridden with increas- 

 ing difficulty by the action of the higher complexes. 



In the brain itself the visual currents may cease to be 

 favorable. There is no longer the desire to see beyond the 



Impulses 

 over associatiorT 

 paths. 'Will* 



''Cerebral 



Motor 



Impulses of" 

 visual oricjir;. 



Impulses of 

 auditory oricjir/. 



Deterrent 



Impulses 



Fiji. 20. To surest, though incompletely, the concentration of 

 certain -tream- of impulses upon the motor cortex in one tired by 

 prolonged exertion. To hrinn in play a fresh |)ath of approach is to 

 secure some renewal of activity. To abate the deterrent impulses 

 has a like effect . 



next turn of the road or to gain the next ridge. What is 

 needed to rouse the flagging cortical centers is stimula- 

 tion over afferent paths that have not yet been brought 

 into use. One of these is the auditory nerve. The ear 

 has had but little to do with reinforcing the walker's 

 efforts up to this time. Hence the mu-ic wakes to ready 

 response a part of the nervous system which has been 

 but little fatigued by any action strictly iN own, although 

 the overflow of fatigue substance- formed elsewhere may 

 have injured it to some extent. The cortical motor 

 neurons are reached over paths nearly inactive until now 



