CHEMICAL CHANGES IN HUMAN BRAIN 469 



8. The data show that, though the absolute amount of each 

 of the constituents added is greatest during a middle period of 

 growth (birth), the greatest rate of growth is in the youngest 

 tissue. It is not believed that brain growth is necessarily auto- 

 catalytic. The whole brain, as well as each constituent, in- 

 creases with development, as is to be expected if it is assumed 

 that a given mass of protoplasm makes more material like itself 

 in an increasingly less favorable environment. It seems to be 

 a logical necessity, not even dependent upon life. 



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