834 PHYSIOLOGY. 



SEVENTH PAIR, FACIAL NERVE, OR PORTIO DURA. 



The facial nerve arises from a nucleus beneath the floor of the 

 fourth ventricle. This nerve contains a motor and a sensory root. 

 The sensory root conies from the cells of the geniculate ganglion, and 

 is called the nerve of Wrisberg. The motor pontal nucleus gives off 

 the neuraxons of the motor root. The motor nucleus is thought to 

 be the upward part of the nucleus ambiguus, which originates the 

 motor fibers in the vagus and glosso-pharyngeal nerves. The neu- 

 raxons of the motor nucleus form a distinct knee, which uprising on 

 the floor of the fourth ventricle is known as the eminentia teres. 

 The facial nerve in its course to the periphery makes a peculiar loop, 

 or knee, inclosing the nucleus of the abducent, and emerges from a 

 depression back of the pons between the olivary and restiform bodies, 

 enters the internal auditory meatus with the auditory nerve, leaves 

 the auditory nerve, enters the Fallopian canal, and makes its exit 

 by the stylomastoid foramen to go to the muscles of the face. The 

 nerve of Wrisberg, or the sensory part of the facial, is made up of 

 neuraxons from the cells of the geniculate ganglion seated in the 

 Fallopian canal. The auditory nerve is also called portio mollis, and 

 it lies to the outer side of the facial, the portio dura, and between 

 the two is the pars intermedia portio inter duram et mollem of Wris- 

 berg, which extends from the medulla to join the facial in the 

 internal auditory meatus. It is connected with both auditory and 

 facial nerves, between which it lies. The central neuraxons of the 

 geniculate ganglion or the nerve of Wrisberg go to the fasciculus 

 solitarius or the vagus and glosso-pharyngeal roots. The peripheral 

 neuraxons of the geniculate ganglion join the facial, and Duval states 

 that they go to form the nerve of taste : the chorda tympani. 



In the hiatus Fallopii the great petrosal nerve branches off from 

 the facial. It, in conjunction with a filament from the glosso-pharyn- 

 geal and another from the sympathetic, passes over to join the gan- 

 glion of Meckel. 



The small pelrosal leaves the aqueduct by a particular opening 

 to end in the otic ganglion. 



Cortical Connection. The motor path from the cortex to the 

 facial nucleus arises from the inferior part of the central con- 

 volutions. 



Chorda Tympani. A few millimeters above the stylo-mastoid 

 foramen the facial gives off a branch of very considerable size: the 

 chorda tympani. It ascends into the cavity of the tympanum. It 



