THE NINTH NERVE 349 



this muscle and divides into branches beneath the hyoglossus. 

 In the jugular foramen it grooves the lower border of the 

 petrous portion of the temporal. 



The upper or jugular ganglion is of small size, and is formed 

 in the outer part of the nerve, some fibers passing over but 

 not joining it. 



The petrous ganglion is larger, and lies in a groove in the 

 petrous bone, involving the entire trunk of the nerve. From 

 it pass the tympanic nerve and branches of communication 

 to the vagus and sympathetic. That to the sympathetic 

 joins the upper cervical ganglion. To the vagus, one joins 

 its auricular branch and one its upper ganglion. Another 

 branch perforates the posterior belly of the digastric, from a 

 point just below the petrous ganglion, to join the facial close 

 to the stylomastoid foramen. 



The tympanic (Jacobson's nerve) runs in a canal in the 

 petrous portion to enter the tympanum through an aperture 

 in its floor close to the inner wall, and divides into branches 

 which groove the promontory and form the tympanic plexus. 

 It gives a branch to the fcnestra rotunda, fcncstra ovalis, and 

 to the Eustachian tube. The nerve finally emerges from the 

 tympanum by a canal at its upper and back part, as the small 

 superficial petrosal nerve. This latter enters the cavity of the 

 skull by a small foramen on the anterior surface of the petrous 

 portion external to the hiatus Fallopii, and escapes by a small 

 foramen in the great wing of the sphenoid, sometimes the 

 foramen ovale, to join the otic ganglion. 



The tympanic nerve sends a communicating branch to the 

 carotid plexus, the small deep petrosal. 



Branches in the Neck. The carotid branches run on the internal 

 carotid to its commencement at the common carotid, joining the 

 pharyngeal branches of the vagus and the sympathetic. 



The pharyngeal, three or four, pierce the superior constrictor 

 to the mucous membrane of the upper pharynx. 



The muscular, to the stylopharyngeus. 



The tonsillitic, to the tonsil and soft palate, form the circulus 

 tonsillaris and join the palatine nerves. 



The lingual are the two terminal branches. One supplies 

 the mucous membrane of the posterior third of the tongue 

 and the circumvallate papillae; the other, to the side of the 

 tongue, joins the gustatory. 



