140 Journal of Comparative Neurology. 



sociated. The remarkable accuracy with which a lost 

 limb will be restored after amputation in many amphibians 

 might be appealed to in the same way. 



Although there may still exist scholastics so blind to 

 the discoveries of the last decades as to scout the interde- 

 pendence of mind and brain, a little study reveals marvel- 

 ous adjustments of bodily functions rivaling the most 

 recondite psychical coordinations. 



A question which has frequently been propounded to 

 the writer is this: Does the brain continue to grow and 

 elaborate cells and fibres after reaching maturity, and, if 

 so, can the individual in any way influence or determine 

 the nature and rate of such growth? 



This is undoubtedly a question of serious import, 

 not only to the. surgeon but to educators and psychologists 

 as well; and, while it is as yet impossible to answer it with 

 as much confidence as could be desired, it may not be 

 amiss to indicate the direction from which the solution 

 may be expected and a few facts and suggestions looking 

 toward that end. Corollaries of the question stated above 

 give rise to the interesting problems respecting the 

 phenomena of senility and decline as well as the physical 

 reasons for the decreasing plasticity and educability 

 of maturity. Much effort has of late been expended 

 in the attempt to demonstrate in the tissues at large 

 processes of senile degeneration — changes in structure 

 corresponding to the limitations in function which experi- 

 ence associates , with the process of growing old. These 

 -investigations appear to have yielded results disappointing- 

 ly small. It would be natural to limit the search specifi- 

 cally to the central nervous system which, as has been 

 seen, exercises a control not merely upon the function but 

 concomitantly upon the growth of the bodily organ. 



Recalling that the origin of all nerve cells is primarily 

 from a proliferating epithelium it would be natural to ex- 



