THE EVOLUTION OF MIND 



modifying the nutrition of his cerebral tissue, 

 must impress itself upon the unstimulated and 

 half- developed brain of his infant offspring. 

 Eliminating the effects wrought in it by count- 

 less environing circumstances, we may say that 

 the infant brain just as surely tends to develop 

 transit lines similar to those in the parental 

 brain as the infant face tends to develop mus- 

 cular peculiarities of expression like those char- 

 acteristic of the parental face. And while the 

 tendency is so slight as to count for little or 

 nothing in the case of the more complex and 

 infrequent associations of ideas, it must be a 

 resistless tendency in the case of those nerve 

 connections which answer to associations in- 

 volved in every act of experience, — as, for ex- 

 ample, those concerned in building up our con- 

 ceptions of space, time, force, and causation. 

 A concise restatement of the case will now lead 

 us at once to our conclusion. While ancestral 

 experience impresses upon the brain a nutri- 

 tive tendency toward the formation of certain 

 special nerve connections, individual experience 

 tends now to assist and now to check the in- 

 herited tendency. And so the number and 

 direction of transit lines in any brain is due to 

 the cooperation of innumerable ancestral and 

 individual experiences. Locke was therefore 

 wrong in calling the infant's mind a blank sheet 

 upon which experience is to write knowledge. 



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