THE CRANIAL NERVES 289 



and is in all probability not sensible to stimulation in any other 

 way. 



Ninth Nerve (Glosso-pharyngeal). 



Origin. The apparent origin of this nerve is from the upper 

 part of the medulla in the groove between the olivary and resti- 

 form bodies. Its deep origin is in the lower part of the floor of 

 the fourth ventricle above the nucleus of the tenth. 



Course and Distribution. Leaving the skull by the jugular 

 foramen, it passes forward between the internal jugular vein and 

 the internal carotid artery, descends in front of the latter to the 

 lower border of the stylo-pharyngeus where it curves inward, 

 runs beneath the hyoglossus, and is distributed to the fauces, pos- 

 terior 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 tonsil and 

 soft palate, the circumvallate papillae and the mucous membrane 

 at the base and side of the tongue and on the anterior surface of 

 the epiglottis. Some of its branches join branches from the 

 pharyngeal and external laryngeal branches of the pneumogas- 

 tric 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 sensi- 

 bility 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 sensibility 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 gusta- 

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

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