344 THE GROWTH OF THE BRAIN. 



are those with strong inherent impulses towards develop- 

 ment. On neurological grounds, therefore, nurture is to 

 be considered of much less importance than nature, 1 

 and in that sense the capacities that we most admire in 

 persons worthy of remark are certainly inborn rather 

 than made. 



Among children there are the widest variations in 

 congenital composition of the central systems, and 

 similarity is neither desirable nor liable to occur save 

 among the members of the same family, or, better still, 

 in cases of twins. It has been made probable that by 

 the cultivating processes of school-training the formed 

 structures tend to be strengthened, dormant elements 

 roused to further growth and organisation, and made 

 more perfect in this or that direction according to the 

 nature of the exercise. By strengthening the formed 

 cells their powers of differential reaction, of organic 

 memory, and resistance to fatigue are increased. By 

 associating given sets of muscular reactions with given 

 sense impressions habits are formed, in consequence of 

 further organisations among the nerve elements, and 

 finally nutritive rhythms associated with the periods of 

 activity and rest are established, with the result of econo- 

 mising the bodily energy, and rendering its expenditure 

 more effective. 



In general the power of sense discrimination increases 

 with age, because such discrimination depends mainly 

 on central arrangements which are not elaborated in the 

 earliest years, but where it depends on peripheral arrange- 

 ments the power may in some cases decrease with age. 

 Thus Czermak 2 has brought forward evidence that the 

 power to discriminate two points on the skin is rather 

 finer in children than in adults, owing to the better 



1 Gallon, Inquiries into Human Faculty, 1883. 



2 Czermak, Gcsammelte Schriftcn, Leipzig, 1879. 



