178 The Unity of the Organism 



this stimulus contraction of the extensor muscles imme- 

 diately succeeds, this "rebound" being especially marked 

 in the vasto-criireus muscle, the main knee extensor. -^^ 



The Antagonisms within the Autonomic System Finally 



Integrative 



It was mentioned above that "cooperative antagonism" in 

 nervous action is widespread in the animal mechanism. The 

 illustrations given pertained to the cerebrospinal system 

 and the innervation of skeletal muscles. We must now fol- 

 low this subject farther and deal with the somewhat similar 

 phenomena presented by the autonomic nervous system. 

 This subject was treated to some extent in the chapter on 

 internal secretions, to the extent, that is, that it implicated 

 the endocrinal glandular system. The presentation here 

 will involve some repetition of what was said in the previous 

 discussion, but the nature and importance of the subject 

 will justify this. 



Cannon appears to have been the first to make clear the 

 similarity between the opposing action of the subdivisions of 

 the autonomic nervous system and what Sherrington calls 

 the reciprocal innervation of antagonistic skeletal muscles. 

 "As the above description has shown," Cannon writes, "there 

 are peripheral oppositions in the viscera corresponding to 

 the oppositions between flexor and extensor muscles." ^^ 



The description referred to is summed up in the state- 

 ment that many of the viscera and other parts of the body 

 are innervated by either the cranial or sacral, i.e., the ter- 

 minal autonomics, and also by the thoracico-lumbar or mid- 

 dle autonomic, this double innervation being such as to be 

 statable thus: ''When the mid-part meets either end-part in 

 any viscus their effects are antagonistic.^' '^'^ The heart- 

 beat is slowed by the cranial autonomic and quickened by the 

 thoracico-lumbar. Contraction of the smooth muscular 



