Chemico-Functioiial Integration 129 



Composition and Nature of the Autonomic System 



The name autonomic was given to this category by Lang- 

 ley. "The autonomic nervous system," he says, "means the 

 nervous system of the glands and of the invohuitary muscles ; 

 it governs the 'organic' functions of the body"; and further: 

 "The word implies a certain degree of independent action, 

 but exercised under the control of a higher power." ^** l^ay- 

 liss adds: "It is necessar}^ to be quite clear that the au- 

 tonomic system includes the sym]:)athetic, since some writers 

 abroad use the name as applying to all the visceral nervous 

 system other than the sympathetic, speaking of sympathetic 

 and autonomic." ^^ 



Perhaps the most important single fact which differen- 

 tiates the autonomic from the cerebro-spinal system is the 

 intercalation, everywhere in the autonomic system, of an 

 extra neurone between the cerebro-spinal ners'e and the part 

 innervated. Cannon states this distinction very clearly : 

 "The skeletal muscles receive their nen-e supply direct from 

 the central nervous system, i. e., the nerve fibers distributed 

 to these muscles are parts of the neurones whose cell-bodies 

 lie within the brain or spinal cord. The glands and smootli 

 muscles of the viscera, on the contrary, are, so far as is now 

 known, never innervated directly from the central nervous 

 s^'stem. The neurones reaching out from the brain or spinal 

 cord never come into immediate relation with the gland or 

 smooth muscle cells ; there are always interposed between the 

 cerebrospinal neurones and the visceral extra neurones 

 whose bodies lie wholly outside the central nervous 

 system." ^^ 



Cannon's suggestion that these interposed neurones may 

 function as transformers for impulses received from the cere- 

 brospinal system should be noted here. 



Three sharp subdivisions of the autonomic nervous sys- 

 tem are recognizable. One is known as the vagal or cranial 



