312 



COORDINATION AND SENSATION 



actions and are under intelligent direction, they are brought 



about in much the same manner. 



Voluntary Action Pathways differ in but one essential 



respect from those of reflex action. They pass through 



the cerebrum, the organ of the mind (Fig. 140). This is 



necessary in order that the 

 mind may control the action. 

 From all portions of the 

 body surface, afferent path- 

 ways may be traced to the 

 cerebrum ; and from the 

 cerebrum efferent pathways 

 extend to all the voluntary 

 organs. A complex system of 

 intermediate neurons, found 

 mostly in the brain, join the 

 afferent with the efferent 

 pathways. The voluntary 

 pathways are not distinct 

 from, but include, reflex 

 pathways, a fact which ex- 

 plains why the same external 



FIG. 140. Diagram of a voluntary 

 action pathway. 



stimulus may excite both 

 reflex and voluntary action 

 (Fig. 141). 



Choice in Voluntary Action. In reflex action a given 

 stimulus, acting in a certain way, produces each time the 

 same result. This is not the case with voluntary action, 

 the difference being due to the mind. In these actions the 

 external stimulus first excites the mind, and the resulting 

 mental processes perhaps as memory of previous experi- 

 ences supply a variety of facts, any of which may act as 

 stimuli to action. Before the action takes place, however, 



