290 THE NERVOUS SYSTEM 



uted to the fauces, posterior third of the tongue, and the 

 tonsil. 



It communicates with the seventh, tenth and sympathetic. 



Its branches of distribution go to the mucous membrane 

 and muscles of the pharynx, the stylo-pharyngeus, the ton- 

 sil and soft palate, the circumvallate papillae and the mucous 

 membrane at the base and side of the tongue and on the an- 

 terior surface of the epiglottis. Some of its branches join 

 branches from the pharyngeal and external laryngeal 

 branches of the pneumogastric to form the pharyngeal 

 plexus. 



Functions. It is the nerve of sensation to the pharynx 

 and fauces and a nerve of taste to the base of the tongue. 

 Its sensibility at its root is dull, but stimulation produces no 

 motion. Although this nerve is distributed to the mucous 

 membrane over the base of the tongue, palate and pharynx, 

 these parts receive the greater portion of their general sen- 

 sibility from filaments of the fifth, and section of the ninth 

 produces no marked effect upon the reflex phenomena of 

 deglutition. The sense of taste is distributed to the anterior 

 two-thirds of the tongue by the chorda tympani, and it has 

 nothing to do with general sensation, while the glosso- 

 pharyngeal, endowing the posterior third with gustatory 

 power, also furnishes to it a degree of general sensibility. 



Tenth Nerve (Pneumogastric, Vagus). 



Origin. This is a mixed nerve. Its apparent origin is 

 from the groove between the olivary and restiform bodies 

 below the ninth! Its deep origin is in the floor of the fourth 

 ventricle just below that of the glosso-pharyngeal. 



Course and Distribution. As it leaves the cranium by the 

 jugular foramen it presents a ganglionic enlargement, the 

 jugular ganglion, or ganglion of the root, just below which 

 it is joined by the accessory portion of the spinal accessory. 

 Below the junction is a second ganglion, the ganglion of the 



