REFLEX ACTION. 623 



intercommunication between the various cells of the cord, and 

 thus make beaten tracks, along which impulses can pass without 

 hindrance. The nerve paths along which the impulses, producing 



FIG. 242. 



Diagram of the paths taken by the impulses in the brain and cord. M M, motor chan- 

 nels ; s s, sensory channels ; cr., cra"hial nerves. 



certain movements commonly performed by every individual, 

 have to pass, are no doubt prepared by the long practice of our 

 ancestors, and the power of performing these actions is trans- 



