134 Cranial Nerves. 



478. The Portio intermedia Wrisbergii after E. Bischoff. 



The s e v e n t li or facial nerve, Nervus facialis, is the great 

 motor nerve of the face. It arises from the lateral tract of the JMedulla 

 oUongata by two roots ; the anterior root from the restiform body, the 

 posterior as Portio intermedia of Wrisberg from the floor of the fourth 

 ventricle. Both trunks lie in a groove of the auditory nerve, with which 

 the Portia intermedia is connected. At the bottom of the internal auditory 

 meatus the facial nerve leaves the auditory ; it enters the Aquaeductus 

 Fall op it and follows the windings of that canal 5 after having passed 

 at first horizontally outwards, it bends sharply backwards, forming 

 the genu; here it presents a reddish enlargement, the geniculate 

 ganglion, Ganglion f/cniculi. This ganglion receives the great superficial 

 petrosal nerve, and a twig of the small superficial petrosal, also filaments 

 from the sympathetic plexus accompanying the middle meningeal artery. 

 From the genu in the Aquaeductus FaUopii, the direction of the canal and the 

 facial nerve lying in it, is backwards and finally downwards to the stylo- 

 mastoid foramen. Behind the genu, two branches are given off from the facial 

 nerve; the smaller, tympanic branch, leaves the facial trunk opposite 

 the pyramid of the tympanic cavity, to supply the stapedius muscle (see 

 Fig. 482); the larger, the Chorda tympani, leaves the trunk above the stylo- 

 mastoid foramen, passes through a small canal, the Canaliculus chordae, into 

 the tympanic cavity, then between the handle of the malleus and long 

 process of the incus to the Glaserian fissure, and finally unites with the 

 lingual nerve, to which it supplies motor fibres. 



