Integrative Systems 183 



that of the connector-neurons. Connector-fibers and exciter-fibers mav 

 be distinguished by the fact that the connectors have the myelin 

 sheath (medidlated fibers) and the exciters are usually nonmedul- 

 lated. 



Distribution of Autonomic Nerves 



The general relations of the several autonomic ganglions are, 

 briefly, as follows (see Figs. 157, 159): 



Ciliary ganglion: connector-fibers enter from cranial nerve III. 

 Exciters pass to smooth muscles of iris (regulating aperture of pupil) 

 and to the accommodatory ciliary muscles within the eye (see p. 201). 



Sphenopalatine ganglion: connectors from VII. Exciters go to 

 lacrimal ("tear") gland and glands of nasal cavity. 



Sublingual and submaxillary ganglions: connectors from VII. 

 Exciters go to, respectively, sublingual and submaxillary salivary 

 glands. 



Otic ganglion: connectors from IX. Exciters go to parotid sali- 

 vary gland. 



The vagus (X), like III, VII, and IX, contains efferent fibers which 

 serve as connectors to autonomic ganglions. Some fibers of the acces- 

 sory nerve (XI) accompany those of X in this distribution. But, in 

 contrast to III, VII, and IX, whose connectors pass to ganglions re- 

 lated to small organs of visceral nature situated in cephalic territory, 

 the vagus assembles its vastly greater number of connectors into the 

 large visceral or intestinal trunk which proceeds backward into 

 thoracic and abdominal territory, where it breaks up into a widely 

 ramifying system of branches, all of which connect with terminal 

 ganglions — i.e., with the intrinsic ganglions and gangliated plexuses of 

 the viscera. In these terminal ganglions, the vagus-fibers make synaptic 

 connection with exciters which pass to smooth muscle-fibers and gland- 

 cells of the various organs. There is reason to believe that in some cases 

 the ganglion may be reduced to its lowest terms, an isolated neuron, a 

 single connector-fiber making synapse with an exciter lying close to the 

 muscle-cell which it excites. It is in this indirect manner, then, that the 

 vagus fibers are related to the motor and secretory effectors of viscera. 

 The major organs thus innervated are the lungs, heart, esophagus, 

 stomach, liver, pancreas, the entire length of the "small" intestine, and 

 the spleen and kidney. 



Lateral ganglions: All of these ganglions contain some exciter- 

 neurons whose fibers distribute to the body-wall. Instead of running 

 out toward the coelomic viscera, a fiber may bend centralwards and 

 enter a ramus communicans, in which it continues back to the point 

 where the ramus emerges from the main spinal nerve. There the fiber 



