THE EDUCATION OF THE NERVOUS SYSTEM. 349 



tactual and visual images, for example, are by no means 

 capable of being manipulated in the same manner, and 

 hence that relations conceivable in the terms of one are 

 often not so in those of the other. With the employ- 

 ment of one sort of mental image comes precision, but 

 it is precision gained at the price of limitations. 

 Fortunately the law of the diffusion of incoming im- 

 pulses works against a too great specialisation in this 

 direction. Yet in the highly defective this specialisa- 

 tion must be carried very far, and in those whose 

 endowments are distinctly unusual the dominance of 

 one sense in controlling the reactions of the central 

 system may rise to the dignity of a deformity. It 

 would be a pallid truism to insist that persons are 

 very different in the anatomy of their nervous system, 

 and also in their nervous activities, were it not that 

 educational practice appears so often to start from quite 

 contrary assumptions. 



The description of racial differences in nervous re- 

 actions forms a literature by itself, and the traits of 

 widely separated classes in the same community are 

 almost as different as those of unlike races. In Bavaria 

 Ranke * found the cranial capacity of the townspeople 

 distinctly greater than that of the peasants in the sur- 

 rounding country a relation which probably means that 

 in general the better endowed individuals sought the 

 severer struggle of the town with its greater excitements 

 and compensations. It is to be anticipated that one 

 great difference in races will be found to lie in the 

 extent of growth and organisation in the nervous system 

 after birth, and especially after puberty. Should it turn 

 out on further examination that some of the lower 

 races lose their capacity for later training after adoles- 

 cence, we should look with interest for the changes in 

 1 Ranke, Der Menscli.^ 1894. 



