CHAP. XX.] THE VAGUS NERVE. 1 1 9 



ramifies, and the remarkable rapidity with which the pharyngeal 

 muscles respond to the slightest stimulus applied to it. 



The following conclusions may be adopted respecting the glosso- 

 pharyngeal nerve. 



1. It is the sensitive nerve of the mucous membrane of the fauces 

 and of the root of the tongue, and in the latter situation it ministers 

 to taste and touch as well as to common sensibility; and being the 

 sensitive nerve of the fauces, it is probably concerned in the feeling 

 of nausea which may be so readily excited by stimulating the mu- 

 cous membrane of this region. 



2. Such are its peripheral organization and central connexions, 

 that stimulation of any part of the mucous membrane in which it 

 ramifies, excites instantly to contraction all the faucial muscles sup- 

 plied by the vagus and the facial nerves, and the permanent irrita- 

 tion of its peripheral ramifications, as in cases of sore throat, will 

 affect other muscles supplied by the facial nerve likewise. It is, 

 therefore, an excitor of the movements necessary to pharyngeal de- 

 glutition. 



Of the Vagus Nerve. The par vagum or pneumogastric nerve, is 

 of all the encephalic nerves the most extentively connected. 



This nerve emerges from the medulla oblongata immediately be- 

 low the glosso-pharyngeal, by from eight to ten fasciculi of fibres 

 which pass outwards to an opening in the dura mater, through which 

 it escapes in company with the spinal accessory. The line along 

 which its fascicles emerge from the medulla is placed a little behind 

 the posterior edge of the olivary body. These fascicles penetrate the 

 olivary columns, and are there implanted in a special accumulation 

 of vesicular matter. 



A ganglion is formed upon the vagus nerve immediately it enters 

 the canal of the dura mater. From this ganglion some small nerves 

 come off. Shortly after the emergence of the vagus nerve from 

 the base of the skull, another gangliform enlargement is formed 

 upon it, which Arnold calls, plexus gangli for mis. It is at the situ- 

 ation of this enlargement that the union between this nerve and the 

 internal branch of the spinal accessory takes place. 



At its upper part the vagus forms numerous anastomoses, at first 

 by nerves given off from the ganglion. These are, a, with the ganglion 

 petrosum of the glosso-pharyngeal, b, with the carotid branch of the 

 superior cervical ganglion, c, with the facial nerve, through the 

 branch called by Arnold the auricular, which is situate in the jugu- 

 lar fossa outside the vein, and is seen through its coats when that 

 vessel is laid open. It anastomoses likewise with the ninth 



