GLOSSO-PHARYXGEAL NERVE. 



617 



pathetic or vice versd, and a third to the ganglion of the root of the pneumo -gastric 

 nerve. The last is not constant. 



There is sometimes likewise a filament from the digastric branch of the facial nerve, 

 which, piercing the digastric muscle, joins the glosso-pharyngeal nerve below the 

 petrous ganglion. 



The tympanic branch (nerve of Jacobson), arises from the petrous ganglion, and is 

 conducted to the tympanum by a special canal, the orifice of which is in the ridge of 

 bone between the jugular fossa and the carotid foramen. On the inner wall of the 

 tympanum the nerve joins with a twig from the sympathetic in a plexus (tym- 

 panic), and distributes filaments to the membrane lining the tympanum and the 

 Eustachian tube, as well as one to the fenestra rotunda, and another to the fenestra 

 ovalis. 



Fig. 415 



Fig. 415. SKETCH OP THE TYMPANIC 

 BRANCH OF THE GLOSSO-PHARYN- 

 GEAL NERVE, AND ITS CONNECTIONS 

 (from Breschet). 



A, squamous part of the left tem- 

 poral bone ; B, petrous part ; C, in- 

 ferior maxillary nerve ; D, internal 

 carotid artery ; a, tensor tympani 

 muscle ; 1, carotid plexus ; 2, otic 

 ganglion ; 3, glosso-pharyngeal nerve ; 

 4, tympanic nerve ; 5, twigs to the 

 carotid plexus ; 6, twig to fenestra 

 rotunda ; 7, twig to fenestra ovalis ; 

 8, junction with the large superficial 

 petrosal nerve ; 9, small superficial 

 petrosal ; 10, twig to the tensor tym- 

 pani muscle; 11, facial nerve; 12, 

 chorda tyrapani ; 13, petrous ganglion 

 of the glosso-pharyngeal ; 14, twig to 

 the membrane of the Eustachian tube. 



From the tympanic nerve are 

 given three connecting branches, 

 by which it communicates with 

 other nerves; and which occupy 

 channels given off from the osseous 



canal through which the nerve enters the tympanum. One branch enters the carotid 

 canal and joins with the (sympathetic on the carotid artery. A second is united to 

 the large superficial petrosal nerve, as this lies in the hiatus Fallopii. And the 

 third is directed upwards, beneath the canal for the tensor tympani muscle, towards 

 the surface of the petrous portion of the temporal bone, where it becomes the small 

 petrosal nerve; and under this name it is continued to the exterior of the skull 

 through a small aperture in the sphenoid and temporal bones, to end in the otic 

 ganglion. As this petrosal nerve passes the gangliform enlargement of the facial, it 

 has a connecting filament with that enlargement, which is by some considered its 

 principal posterior termination. 



Jacobson described an anterior or internal branch from the tympanic nerve to the 

 spheno-palatine ganglion. 



BRANCHES DISTRIBUTED IN THE NECK. 



The carotid branches course along the internal carotid artery, and unite with the 

 pharyngeal branch of the pneumo-gastric, and with branches of the sympathetic. 



The pharyngeal branches, three or four in number, unite opposite the middle con- 

 strictor of the pharynx with branches of the pneumo-gastric and sympathetic to form 

 the pharyngeal plexus. Nerves to the mucous membrane of the pharynx perforate 

 the muscles, and extend upwards to the base of the tongue and the epiglottis, and 

 downwards nearly to the hyoid bone. 



