782 



THE NEKVOUS SYSTEM. 



Branches and Communications. (i.) In the internal acoustic meatus the nervus 

 intermedius, lying between the facial and acoustic nerves, sends communicating 

 branches to both of them. The branch to the acoustic nerve probably separates 

 from it again to join the genicular ganglion of the facial nerve. 



(ii.) In the canalis facialis the ganglion geniculi is formed at the point where 

 the facial nerve bends backwards. It is an oval swelling on the -nerve, and is 

 joined by a branch from the upper (vestibular) trunk of the acoustic nerve, by 

 which it probably receives fibres of the nervus intermedius. From the ganglion 

 three small nerves arise : (1) The greater superficial petrosal nerve passes forwards 

 through the hiatus canalis facialis to the middle fossa of the skull. In the 

 upper part of the foramen lacerum it is joined by the deep petrosal nerve 

 from the sympathetic plexus on the internal carotid artery to form the nerve 

 of the pterygoid canal, which, after traversing the pterygoid canal, ends in the 

 spheno- palatine ganglion. (2) A minute nerve (ramus anastomoticus cum plexu 

 tympanico} pierces the temporal bone and joins the tympanic branch of the glosso- 



Anastornotic with tympanic plexus 



Tympanic plexus v i 



Chorda tympaui , \ 



Nerve to stapedius \ \ \ 



Genicular ganglion 



Facial nerve 

 I Nervus intermedius 

 / | Acoustic nerve 



External superficial petrosal nerve 

 ,1 Greater superficial petrosal nerve 

 Carotico-tyin panic nerve 

 Smaller superficial petrosal nerve 



Sympathetic plexus on internal carotid artery 



Spheno-palatine brai 

 Maxillary nerve 

 | Spheno-palatii 

 branches 



Posterior auricular nerve / / 



rves.to stylo-hyoid and digastric (posterior belly) 

 Communication with auricular branch of vagus' 



Auricular branch 



Vagus nerve, jugular ganglioi: 



Glossopharyngeal nerve 



Tympanic branch 

 Auriculo-teuiporal nerve 



External super- 

 ficial petrosal nerve . 



Sympathetic plexus on Spheno-palatin 

 middle meningeal artery 

 "Otic ganglion 



"ZirJ }Communication to roots of auriculo-tempo 



I Communication to chorda tympani 



- Mandibular nerve 



Masticator nerve (anterior division of mand 



Lingual nerve 



Inferior alveolar nem 



FIG. 656. THE CONNEXIONS OF THE - FACIAL NERVE IN THE TEMPORAL BONE. 



pharyngeal in the substance of the bone. By their union the lesser superficial 

 petrosal nerve is formed, which pierces the temporal bone and ends in the otic 

 ganglion. (3) The external superficial petrosal nerve is a minute inconstant branch 

 which joins the sympathetic plexus on the middle meningeal artery. 



In the course of the facial nerve in the lower part of the canalis facialis, 

 behind the tympanum, three branches arise (1) N. Stapedius. The small nerve 

 to the stapedius muscle, which passes forwards to the tympanum. (2) Chorda 

 Tympani. The chorda tympani nerve (probably associated with the nervus inter- 

 medius), which enters the tympanic cavity through the tympanic aperture of the 

 canaliculus chordce, passes over the membrana tympani and the handle of the 

 malleus, and leaves the cavity through the medial end of the petro-tympanic fissure 

 to reach the infra -temporal fossa. Medial to the external pterygoid muscle it 

 becomes incorporated with the lingual branch of the mandibular nerve, and in its 

 further course is inseparable from that nerve. It supplies a root to the submaxillary 

 ganglion, and is finally distributed to the side and dorsum of the tongue in its 

 anterior two-thirds. The chorda tympani nerve receives, under cover of the ex- 

 ternal pterygoid muscle, a fine communication from the otic ganglion. (3) Before 

 it leaves the canalis facialis a fine communicating branch arises from the facial 

 nerve to join the auricular branch of the vagus nerve. 



(iii.) In the neck the facial nerve gives off three muscular branches : (1) and (2) 



