CEREBRUM AND THE LIFE OF THE INDIVIDUAL 157 



maturely this rigidity, which must in any event arrive at 

 last unless death anticipates it. 



The hardening of the arteries in later years is an im- 

 portant and widely discussed feature of the senile decline. 

 Portending the day when " the pitcher shall be broken 

 at the fountain or the wheel broken at the cistern," it 

 is a material type of the invisible change in the constitu- 

 tion of the central gray matter which gradually limits its 

 capacity to respond to new exactions. Much as arterio- 

 sclerosis can be postponed by temperance in eating and 

 drinking and by a wise ordering of all the activities of 

 life, so the loss of plasticity in the cortical organization 

 can be delayed by the same temperate conduct with the 

 added element of a studied variety in its employment. 

 It seems to be much more within our power to do this 

 than to prevent the inevitable stiffening of the crystalline 

 lens which abolishes the accommodation for near vision 

 at about the same period for all persons with normal 

 eyes. 



It will be gathered from what has been said that if the 

 young nervous system excels the older one in its capacity 

 for variation in reaction, the older one surpasses the 

 younger in its confinement of its energies to profitable 

 channels. It is the more economic of the two. This 

 is much like saying that it has the greater exercise of in- 

 hibition. In it, wasteful diversions of nerve-currents to 

 call info play effectors which serve no useful purpose have 

 become reduced to a minimum. When a child no longer 

 cries when matters are not altogether to its liking and, 

 instead, seeks compensations in each situation, it has sup- 

 pressed or inhibited a lower type of reaction in favor of a 

 higher one. The progress of education always continues 

 to be marked by such substitutions. 



This inhibition of primitive reactions by others based 

 upon complex experiences is best illustrated by the human 

 being, but is not wholly wanting in the most intelligent 

 of the lower animals. The dog that endures abuse at the 

 hands of children without turning upon its tormentors 



