558 THE NE'RVOUS SYSTEM 



the spheno-palatine ganglion. After communicating with the vagus and, 

 soon after it leaves the cranium, with the sympathetic, with the digastric 

 branch of the facial, and the accessory nerve, the glosso-pharyngeal divides 

 into the two principal divisions indicated by its name, which supply the mucous 

 membrane of the posterior and lateral walls of the upper part of the pharynx, 

 the Eustachian tube, the arches of the palate, the tonsils and their mucous 

 membrane, and the tongue as far forward as the foramen cecum in the middle 

 line, and to near the tip at the sides and inferior part. 



Functions. The glosso-pharyngeal nerve contains some motor fibers, 

 together with fibers of common sensation and the sense of taste. 



Motor fibers are distributed to the palato-pharyngeus, the stylo-pharyngeus, 

 palato-glossus, and constrictors, of the pharynx. 



Sensory fibers of touch and of common sensation are distributed to the 

 pharynx, the tonsils, and posterior palate. Nerves of taste are supplied to 

 the taste buds on the posterior third of the tongue and to the fauces. 



The Tenth Nerve, Vagus or Pneumogastric Nerve. The origin of the 

 vagus nerve is, as we have just seen, situated in the lower half of the floor of 

 the fourth ventricle, figure 374. Its nucleus is said to represent the cells of 

 Clarke's column of the spinal cord. In origin it is closely connected with 

 the ninth, eleventh, and the twelfth. The combined glosso-pharyngeal-vago- 

 accessory nuclei lie outside of, close to, and parallel with the nucleus of the 

 twelfth. There are two main vagal nuclei: one motor, the other sensory. 



Distribution. It has, of all the nerves, the most varied distribution and 

 functions, either through its own filaments, or through those which, derived 

 from other nerves, are mingled in its branches. The vagus supplies sensory 

 branches, which accompany the sympathetic on the middle meningeal artery, 

 and others which supply the back part of the meatus and the adjoining part 

 of the external ear. It is connected with the petrous ganglion of the glosso- 

 pharyngeal, by means of fibers to its jugular ganglion, \vith the spinal acces- 

 sory, which supplies it with its motor fibers for the larger and upper portion 

 of the esophagus, and with its inhibitory fibers for the heart; also with the 

 twelfth; with the superior cervical ganglion of the sympathetic; and with the 

 cervical plexus. The parts supplied by the branches of the vagus are as 

 follows: 



1 . A large portion of the mucous membrane and probably all the muscles 

 of the pharynx are supplied by its pharyngeal branches. 



2. The mucous membrane of the under surface of the epiglottis, and of 

 the greater part of the larynx, and the crico-thyroid muscle, by the superior 

 laryngeal nerve. 



3. The mucous membrane and muscular fibers of the trachea, the lower 

 part of the pharynx and larynx, and all the muscles of the larynx except the 

 crico-thyroid are supplied by the injerior laryngeal nerve. It also supplies 

 the first segment of the esophagus. 



