944 



THE NERVOUS SYSTEM 



the arachnoid and the dura mater and enters the facial canal (aqueduct of Fallo- 

 plus), in which it runs forward and slightly lateral ward to the hiatus Fallopii, 

 where it makes an angular bend, the external genu [geniculum], around the 

 anterior boundarj^ of the vestibule of the inner ear; this bend is enlarged by the 

 adhesion of the geniculate ganglion (of the glosso-palatine) upon its anterior 

 border. From the geniculum the facial nerve runs backward in the facial canal 

 along the lateral wall of the vestibule and the medial wall of the tympanum, above 

 the fenestra vestibuli (ovalis), to the junction of the medial and posterior walls of 

 the tympanic cavity; then, bending downward, it descends in the posterior wall 

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

 foramen it turns forward around the lateral side of the base of the styloid process, 



Fig. 738. — Diagram of the Facial (Yellow) and Glosso-palatine Nerve (Blue). 



Fibres from oc- __^ ^^^^^^ canal 



ulomotor nerve 



Nucleus of 



abducens nerve 



Nucleus of „ 

 facial nerve 



Glosso- 

 palatine 

 Internal 

 auditory 

 meatus 

 Small superficial 

 petrosal nerve 

 Fenestra vestibuli 

 Tympanic plexus 



Chorda tympam 



Communication to 



auricular branch 



of vagus 



Fenestra cochleae 



Posterior auricular 



Communication to 



glosso-pharyngeal 



nerve 



Nerve to post, belly 



of diagastric 



Nerve to stylo- 

 hyoideus 



Maxillary 

 nerve 

 Spheno- 

 palatine 

 ganglion 

 Vidian nerve 



Great deep 

 petrosal nerve 

 Middle meningeal 



Foramen ovale artery 



Otic ganglion 



Spine of sphenoid 

 Communication from auriculo- 

 temporal 

 Chorda tympani 



Communication from auricular 

 branch of glosso-pharyngeal 



Lingual nerve 



Styloid process 

 Tympanic branch of facial nerve 



Small deep petrosal nerve 



and plunges into the substance of the parotid gland, where it divides into its 

 cervico-facial and temporo-facial terminal divisions. Before its terminal divisions, 

 the nerve gives off three, and sometimes four, small branches: one, the nerve to 

 the stapedius muscle, before it leaves the skull, the others after it leaves the skull. 



'The nerve to the stapedius is given off from the facial nerve as it descends in the posterior 

 wall of the tyinpanum behind the pyramidal eminence. It is stated that filaments are also 

 given off fron) the facial to the auditory artery (probably visceral motor from the glosso-palatine) 

 while the nerve is i^assing thi'ough the internal auditory meatus. 



After it leaves the skull the facial nerve gives off two or three collateral 

 branches and its two terminal divisions, the temporo-facial and cervico-facial. 

 The collateral branches are th(! posterior auricular nerve, a branch to the posterior 

 belly of the digastric, and sometimes a lingual branch. 



(1) The posterior auricular nerve is the first branch of the extracranial portion of the facial 

 nerve. It i)asses b(3tween the parotid gland and the anterior border of the sterno-mastoid 

 muscle and runs ujjward in the deep interval between the external auditory meatus and the 

 mastoid process. In this situation it communicates with the auricular branch of the vagus. 

 It supplies the auricularis posterior, sends a slender twig upward to the auricularis superior, 

 and ends in a long slender branch, the occipital branch, which passes backward to supply the 

 occipitalis muscle. It also receives filaiiiciils from t Ik; small occipital and great auricular nerves, 

 and siipi)hes the intrinsic n)usclcs of the; auricle (pinna). 



(2) 'i'lie nerve to the posterior belly of the digastric arises from the facial nerve close to 

 the stylo-mastoid fcjraincn and enters tlie muscle near its (HMitre, or sometimes near its origin. 

 It usually gives off two branches: the nerve to the stylo-hyoid, which sometimes arises directly 

 from the facial n(!rv(! and pas.scs to th(^ upper i)art of the inus(;le that it supplies, and the anas- 

 tomotic branch, wliicli joins the gloss()-])liaryngeal nerve below its petrous ganglion. 



(■i) The lingual branch, first described by Cruveilhier, is not commoidy i)re,sent. It arises 

 a little below the nerve to the stylo-hyoideus and runs downward and medialward to the base 

 of the tongue. In its course it passes to the medial sides of the stylo-glossus and stylo-pharyn- 



