34 2 THE GROWTH OF THE BRAIN. 



certain and precise is our thought. For this reason the 

 development of the intelligence is associated with the 

 perfection of more than one sense organ, whereas 

 reliance on a single avenue of sense, while it may lead 

 to very precise reactions graded in accordance with the 

 intensity of the single sort of stimulus, leaves us without 

 those fringing sensations which form the basis for dis- 

 tinction and comparison. 



In biological equations the values of the different 

 factors are often open to wide variation. We have 

 insisted on the three-fold composition of the central 

 system, one factor being afferent or sensory, another 

 central or distributive, and the third motor or efferent ; 

 each one of these divisions represented by distinct 

 anatomical cell groups. It is readily seen that a high 

 degree of responsiveness among the central cells gives 

 us the intellectual type of reaction. Where the efferent 

 portion is well organised, we have the anatomical con- 

 ditions, or the man of affairs or action, while exaggera- 

 tion of the afferent or sensory component leads to a 

 merely passive existence, or to hysteria, according to 

 circumstances. 



Connections between the exercises of formal educa- 

 tion and brain change have not been demonstrated. 

 It is not known how a year's schooling affects the 

 central system, and it is not probable that we shall 

 soon arrive at facts of this sort. Available, however, 

 are the facts of anatomical growth during this period, 

 and to these plausible explanations have been given. 



The aim at the moment, therefore, is to determine 

 what limitations anatomy places to the educational 

 process, and thus to obtain a rational basis from which 

 to attack many of the pedagogical problems. It ap- 

 pears probable that the education of the schools is but 

 one, and that, too, rather an insignificant one, of many 



