Neural Integration 171 



The Spreading and Compoiindijig of Reflexes 



As a practical matter study of tlie intcfrratlvL' action of 

 the nervous systems never gets away from integration among 

 reflex-arcs and reflexes any more than it docs from tlie 

 cellular intergration fundamental to the reflex-arc itself. 

 The general nature of the study always involves the "spread 

 of reflexes over a wide range of nervous arcs." The idea 

 is more fully stated in the following: "This compounding of 

 reflexes with orderliness of coadjustment and of sequence 

 constitutes coordination, and want of it inco-ordination. 

 We may therefore in regard to coordination distinguish 

 coordination of reflexes simultaneously proceeding, and co- 

 ordination of reflexes successively proceeding. The main 

 secret of nervous coordination lies evidently in the com- 

 pounding of reflexes." ^ For the rest, all we can do or need 

 do to meet the requirements of this discussion is to get at 

 the main principles as illustrated by examples of this com- 

 pounding of reflexes. 



As a starting point for the discussion of this larger 

 aspect of neural integration, Sherrington takes what he has 

 called "the principle of the common path." Basal to this 

 conception is the famihar fact that a stimulus applied at a 

 single point, on the surface of the body, for example, gives 

 rise to a nerve impulse which may reach a great number 

 of muscles or glands. A single receptor with its neurone 

 must be in communication with a great number of effectors, 

 some of which are very diff'erent in kind. Looking at the 

 arcs from the efl'ector ends, as one may say, it is obvious 

 that the impulses reaching innumerable eff'ectors must come 

 over a single conducting course. 



On the other hand, since a given muscle or gland may be 

 reached by impulses from a great number of reflex-arcs, 

 the efl*ector and its neurone must })e the "common patli" 

 for all these impulses, often very different in quality and 



