CEREBROSPINAL NERVES 395 



gives its ultimate fibres to the cheeks, nostrils, and lips. A branch 

 from this nerve joins the infra-orbital nerve, and is distributed to the 

 upper lip. 



Eighth, the Auditory Nerve, arises in compau}- with the seventh 

 nerve from the medulla oblongata, immediately behind the pons varolii. 

 It enters the internal auditory meatus at once, and divides into two 

 branches, one of which is supplied to the cochlea and the other to the 

 vestibule and semicircular canals. 



This nerve is for the special sense of hearing. 



Ninth, Glosso-pharyngeal. — This nerve arises from the outer edge 

 of the medulla oblongata, and passes from the cranium through the back 

 part of the foramen lacerum basis cranii. At this point it has upon it 

 Andersch's ganglion, from which the nerve of Jacobson is derived. 



It now descends behind the great cornu of the hyoid bone to reach the 

 base of the tongue, where it supplies filaments to the mucous membrane 

 and sends others to the muscles of the pharynx. 



Branches given ofi" in its course: — A very fine filament (Jacobson's 

 nerve), which enters a small foramen in the petrous portion of the temjioral 

 bone to be distributed to the tympanum. 



Two or three filaments to the superior cervical ganglion. 



A branch which, with some sympathetic filaments, go to the connnon 

 carotid. 



A pharyngeal branch. This passes to the upper wall of the pharynx, 

 and, with the pharyngeal filaments of the pneumogastric and sympathetic 

 nerves, forms a somewhat intricate plexus. 



Tenth, Pneumogastric or Vagus. — This is a most important nerve, 



not only on account of its wide distribution, but equally so in reference to 

 the variety and complexity of its functions. 



It is a mixed nerve, and arises from the side of the medulla olilongata 

 immediately behind the ninth nerve. It then passes out of the cranium 

 through the posterior pai't of the foramen lacerum basis cranii, where it 

 joins the inner division of the eleventh nerve, with which it unites for 

 about an inch of its course. 



In the foramen the nerve presents an enlargement — the jugular gan- 

 glion. This gives off the auricular branch of the vagus, which enters the 

 aqueduct of Fallopius to join the seventh nerve, and subsequently passes 

 out with it to be distributed to the lining membrane of the external 

 auditory canal. Below the occipital artery it becomes united with the 

 cervical sympathetic cord, and joined in this way it passes down the neck 

 with the carotid artery as far as the entrance to the chest, where it resumes 

 its independence. From this point it passes onwards above the division 



