THE HEAD AND NECK 1297 



canal, and it may furnish a petrosal branch to accompany the 

 great deep petrosal nerve. 



For the cavernous part of the internal carotid artery, see p. 1078 . 



Petrous Part of the Faeial Nerve. — This part of the nerve extends 

 from the orifice of the meatus auditorius intemus, on the posterior 

 surface of the petrous part of the temporal bone, to the stylo- 

 mastoid foramen, and it traverses (i) the meatus auditorius intemus, 

 and (2) the aqueduct of Fallopius. 



Meatal Portion. — ^This portion of the nerve is directed outwards, 

 and is accompanied by the pars intermedia of Wrisberg, the 

 auditory nerve, and the internal auditory artery. It is placed upon 

 the upper and anterior aspect of the auditory nerve, and the pars 

 intermedia lies between the two, and here joins the facial nerve. 

 At the deep end of the internal auditory meatus the facial nerve 

 parts company with the auditory nerve, and enters the aqueduct of 

 Fallopius. 



Branches. — ^Two branches connect the facial nerve with the 

 auditory nerve. 



Portion in the Aqueduct of Fallopius. — ^The direction of this portion 

 of the nerve corresponds to that of the aqueduct. It may con- 

 veniently be divided into three stages — first, second, and third. 

 In the first stage, which is very short, the nerve passes horizontally 

 outwards, between the cochlea and vestibule, to the inner wall of 

 the t\TTipanum, where it presents an enlargement, called the 

 geniculate ganglion. It then describes a sharp bend, and in the 

 second stage passes backwards, lying abov^e the fenestra ovalis. 

 Thereafter it describes another abrupt bend, and in the third stage 

 descends behind the posterior wall of the t^Tnpanum to the stylo- 

 mastoid foramen, by which it escapes from the aqueduct. The hiatus 

 Fallopii leads from near the commencement of the aqueduct to the 

 superior surface of the pars petrosa . As the aqueduct descends it com- 

 municates with the canal of the pyramid of the tjTnpanum, and 

 below this it presents another opening, called the iter chordce poster ius. 



Branches. — ^These are as follows : 



{Great superficial petrosal (to Meckel's ganglion). 

 Communicating branch to small superficial petrosal (to the otic 

 ganglion). 

 External superficial petrosal (to sympathetic plexus on middle 

 meningeal artery). 



Nerve to the stapedius muscle. 

 Chorda tympani nerve. 



Communicating branch to the auricular branch (Arnold's nerve) 

 of the pneumogastric. 



The great superficial petrosal nerve arises from the geniculate 



ganglion and passes forwards through the hiatus Fallopii, by 

 which it emerges from the aqueduct of Fallopius. It then courses 

 inwards and forwards in a groove on the superior surface of the 

 petrous part of the temporal bone, and passes beneath the 

 Gasserian ganglion to the foramen laeerum medium. In the upper 



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