976 



THE NERVOUS SYSTEM 



anterior border. From the geniculum it runs dorsalwards in the facial canal along 

 the outer wall of the vestibule and the inner wall of the tympanum, above the fenestra 

 vestibuli (ovalis), to the junction of the inner and posterior walls of the tympanic 

 cavity; then, bending downwards, it descends in the posterior wall to the stylc- 

 mastoid foramen. As soon as it emerges from the stylo-mastoid foramen it turns 

 forwards around the outer side of the base of the styloid process, and plunges into 

 the substance of the parotid gland, where it divides into its cervico-facial and 

 temporo-facial terminal divisions. 



The Sensory Root (the pars intermedia or nerve of Wrisberg). The fibres of the 

 sensory root spring from the cells of the geniculate ganglion, which is situated in the 

 facial canal (aqueduct of Fallopius) immediately behind the hiatus Fallopii. The 

 central processes pass inwards in the trunk of the nerve along the facial canal to the 

 internal auditory meatus, where they leave the trunk and form the pars intermedia, 

 which passes inwards in the meatus and then slightly downwards in the posterior 

 fossa of the cranium to the medulla, which it enters immediately below the lower 

 border of the pons and between the motor root of the seventh nerve and the entering 

 roots of the acoustic nerve. After entering the medulla the fibres pass backwards 



riBKES FROM 

 THIKU XKR YE 



M't'LKUS OF 



SIXTH XERVS 



FIG. 704. DIAGRAM OP THE SEVENTH NERVE. 



FACIAL CANAL 



GEXICULATE GANGLION 



EXT. SUPERF. PETROSAL 



CA TIOX TO 



AURICULAR RRAXCH 

 OF VAGUS 

 FEXESTRA COCHLEA 



POSTERIOR AURICULAR 



COM.VrmC.\TIOX TO 

 XIX TH XERVS 



NERVE TO POUT. KELLY 

 OF DIAGASTRIC 



SERVE TO STYLO- 

 HYOIDEUS 



FORAMKX 

 ROTUNIJUJf 



MAXILLARY 

 KER VK 



MSCKJSV8 



GANGLION 



VIDIAX NERVE 



GREAT i>i':i:r 



1'KTROSAL NERVE 



. ,/./? /'oningeal 

 artery 



SPINE OF SPHENOID 



I'll tnll SICATION FROil AURICULO- 

 '' /. 



TYMPAXI 



I'll l/.l/r.Y/r.l TlflX FROM 

 SIXTH A niKTLAR 



LINGl'AL KERVE 



STYI.OTTI PROCESS 

 TYMPANIC BRANCH OF SEVENTH NERVE 



SMALL DEEP PETROSAL NERVE 



and inwards in the reticular formation, and they terminate in the upper extension 

 of the nucleus of termination of the glossopharyngeal nerve. The sensory root or 

 pars intermedia contains a few motor fibres probably acquired during its blending 

 with the motor root. It is, therefore, somewhat mixed in function. 



The geniculate ganglion is embedded in the anterior border of the geniculum of 

 the seventh nerve behind the hiatus Fallopii. It gives origin to the greater part of the 

 pars intermedia or sensory root of the seventh nerve. Its anterior angle is connected 

 with the great superficial petrosal nerve, and its external angle is connected with 

 fibres which afterwards leave the seventh nerve in its chorda tympani branch (fig. 704). 



Communications and Branches. (a) In the internal auditory meatus the 

 pars intermedia gives two delicate filaments to the vestibular division of the audi- 

 tory nerve, and it is stated that filaments are also given from the facial to the auditory 

 artery and to the temporal bone. 



(b) In the facial canal five important branches are given off, and a communica- 

 tion is received from the sympathetic on the middle meningeal artery. 



(1) The Great Superficial Petrosal Nerve has been described in detail as a root 

 of the spheno-palatine ganglion (p. 972) . It arises from the geniculate ganglion of the 

 seventh nerve, enters the middle fossa of the cranium through the hiatus Fallopii, 



