872 INFLUENCE OF NERVES ON NUTRITION. [BOOK n. 



basis. All biological studies teach us that the growth, repair, and 

 reproduction of living substance may go on quite independently of 

 any nervous system. The white blood corpuscles go through 

 their cycles unmoved by nervous impulses, and the nutrition of 

 the nervous system itself cannot be dependent on the action of 

 that system on itself. All that is really needed to explain these 

 phenomena is an acceptance of the view that a nervous impulse 

 may modify the metabolic events of other tissues than muscles and 

 glands, and may modify them in various ways ; and further that 

 the nutrition of each tissue is in the complex animal body so 

 arranged to meet the constantly recurring influences brought to 

 bear on it by the nervous system, that, when those influences 

 are permanently withdrawn, it is thrown out of equilibrium ; its 

 molecular processes, so to speak, then run loose, since the bit has 

 been removed from their mouths. And as our knowledge of 

 metabolic processes on the one hand and of the actions of the 

 nervous system on the other hand increases, these suppositions 

 become more and more reasonable. 



