312 INTRODUCTION TO NEUROLOGY 



The normal newborn child brings into the world an inherited 

 form of body and brain and a complex web of nerve-cells and 

 nerve-fibers which provide a fixed mechanism, common except 

 for minor variations to all members of the race alike, for the 

 performance of the reflex and instinctive actions. The pat- 

 tern of this hereditary fabric can be changed only very slowly 

 by the agency of selective matings and other strictly biological 

 factors or by degenerations of a distinctly pathological sort. It is 

 thus manifest that the improvement of the racial stock of normal 

 individuals by the practice of eugenics must necessarily be very 

 slow, though the improvement of defective or pathological strains 

 by selective matings so as to breed out the objectionable charac- 

 teristics is fortunately in most cases more readily accomplished. 



But in addition to this hereditary organization the newborn 

 child possesses the large association centers of the brain with 

 their vast and undetermined potencies, the exact form of whose 

 internal organization is not wholly laid down at birth, but is 

 in part shaped by each individual separately during the course of 

 the growth period by the processes of education to which he is 

 subjected, that is, by his experience. This capacity for indi- 

 viduality in development, this ability to profit by experience, 

 this docility, is man's most distinctive and valuable character- 

 istic. And since the form which this modifiable tissue will take 

 is determined by the environing influences to which the child 

 is subjected, and since these influences are largely under social 

 control, it follows that human culture can advance by leaps and 

 bounds wherever a high level of community life and educational 

 ideals is maintained. 



So well have we learned the lesson that the child brings with 

 him into the world no mental endowments ready-made no 

 knowledge, no ideas, no morals but that these have to be 

 developed anew in each generation under the guiding hand of 

 education, that we devote one-third of the expected span of life 

 of our most promising youth to the educational training neces- 

 sary to ensure the highest possible development of the latent 

 cultural capacities of these association centers of the cerebral 

 cortex. 



But we have often been blind to the other side of the picture. 

 We have seen above that the adult cortex cannot function save 



