742 



THE NERVOUS SYSTEM. 



The tympanic branch arises from the nerve opposite the pyramid ; it passes 

 through a small canal in the pyramid and supplies the Stapedius muscle. 



The chorda tympani is given off from the facial as it passes vertically down- 

 ward at the back of the tympanum, about a quarter of an inch before its exit 

 from the stylo-mastoid foramen. It passes from below upward and forward in a 



To Auditory\ 



Geniculate 

 Ganglion, 



Vidian. 

 Large Deep Petrosal 



Tympanic of 

 Giosso-pharyngcal 



Post 



Auricular 



Digastric 

 Stylo-hyoid- 



Ccr 



FIG. 400. Plan of the facial nerve. 



Supramaxillary 

 InframaxiUary 



distinct canal, and enters the cavity of the tympanum through an aperture (iter 

 chordce posterius) on its posterior wall between the opening of the mastoid cells 

 and the attachment of the membrana tympani, and becomes invested with mucous 

 membrane. It passes forward through the cavity of the tympanum, between the 

 fibrous and mucous layers of the membrana tympani, and over the handle of the 

 malleus, emerging from that cavity through a foramen at the inner end of the 

 Glaserian fissure, which is called the iter chordce centering, or canal of Huguier. 

 It then descends between the two Pterygoid muscles, meets the lingual nerve 

 at an acute angle, and accompanies it to the submaxillary gland ; part of it 

 then joins the submaxillary ganglion ; the rest is continued onward through the 

 muscular substance of the tongue to the mucous membrane covering its anterior 

 two-thirds. A few of its fibres probably pass through the submaxillary gang- 

 lion to the sublingual gland. Before joining the lingual nerve it receives a small 

 communicating branch from the otic ganglion. As already stated, the chorda 

 tympani nerve is by many regarded as the continuation of the pars intermedia 

 of Wrisberg. 



The Posterior auricular nerve arises close to the stylo-mastoid foramen, and 

 passes upward in front of the mastoid process, where it is joined by a filament from 

 the auricular branch of the pneumogastric, and communicates with the mastoid 

 branch of the great auricular and with the small occipital. As it ascends between 

 the meatus and mastoid process it divides into two branches. The auricular branch 

 supplies the Retrahens auriculum and the small muscles on the cranial surface of 

 the pinna. The occipital branch, the larger, passes backward along the superior 

 curved line of the occipital bone, and supplies the occipital portion of the Occipito- 

 frontalis. 



