216 DOCTRINE OF EVOLUTION 



structed in one way into a tissue-mechanism of a more 

 complex nature, provides the most conclusive evidence 

 of the reality of brain evolution, because the process of 

 transformation actually takes place. 



But in the present connection we are more interested 

 in the dynamic or functional aspects of mental evolu- 

 .tion, which it must be remembered are inseparably 

 bound up with the physical structures and their modi- 

 fications. After a human infant is born its activities 

 are reflex and mechanical like those of the adult mem- 

 bers of lower groups. As it grows it performs instinc- 

 tive acts because its inherited nervous system operates 

 in the purely mechanical manner of a lower mammal's 

 nervous system. For th'ese reasons an eminent psy- 

 chologist has said that the mental ability of an infant 

 six months old is about that of a well-bred fox terrier. 

 The same infant at nine months displays an intelligence 

 of a higher order equal to that of a well-trained chim- 

 panzee ; it has become what it was not,, and in so far 

 it has truly evolved in mental respects. At two years 

 of age the child is incapable of solving problems of the 

 calculus, for its reasoning powers are elementary and 

 restricted, but these same powers change and intensify 

 so as to render the older mind quite capable of grasping 

 the highest of human conceptions and ideas. In my 

 judgment the unbroken transformation of a child's 

 mind that exhibits only instinct and intelligence into 

 an adult's mind with its power of reasoning, is far more 

 conclusive as proof of mental evolution than the infer- 

 ence drawn from the comparisons we have made above 

 of the adult psychological phenomena of man, ape, cat, 

 and fish. It is surely natural for such mental trans- 



