ORGAN OF HEARING. 



555 



periorly, and which opens on the surface of the 

 petrous bone outside, and in front of the hiatus 

 of Fallopius. From this the nerve advances 

 between the anterior margin of the petrous 

 bone and the posterior angle of the great wing 

 of the sphenoid, between the internal muscle 

 of the malleus and the superficial petrosal 

 nerve. There it approaches the nerve of the 

 internus mallei, and proceeds parallel with it, 

 and under the name of nervus petrosus superfi- 

 cial^ minor Anwldi,* goes to join the otic 

 ganglion. 



Fig. 260. 



Nervous plexus of the tympanum (from Breschet.)'^ 



a. Internal carotid artery ; b. glosso-pharyngeal 

 nerve ; c. petrous ganglion of the same nerve ; 

 d. the principal trunk of the nervous plexus of the 

 tympanum which extends to join, e. the otic gang- 

 lion or ganglion of Arnold ; f, lower maxillary 

 nerve to which the ganglion adheres ; g. filaments 

 of communication between the nerve of Jacobson 

 and the carotid plexus; h. carotid plexus; i. fila- 

 ment to the fenestra rotunda, or cochlear fenestra ; 

 k. filament to the vestibular fenestra; /.filament 

 going to anastomose with the facial nerve ; m. fila- 

 ment running alongside the Eustachian tube ; 

 7i. portio dura of the seventh pair ; o. chorda tym- 

 pani cut ; p. nervous filament from the otic gang- 

 lion to the muscle of the malleus. 



The branches given off and the communica- 

 tions formed by the tympanic nerve in the course 

 described, are the following. On entering the 

 tympanum, the tympanic nerve divides into 

 two branches, a lower and an upper. The 

 lower branch first gives twigs to the Eustachian 

 tube, and then passes out of the cavity of the 

 tympanum into the carotid canal, through a 



* Bidder (Neurologische Beobachtungen. Dor- 

 pat, 1836,) has recently discovered a new nervus 

 petrosus superficialis, which, for the sake of distinc- 

 tion, he calls tertius. It proceeds from the plexus 

 accompanying the middle meningeal artery into the 

 cavity of the cranium, passes through a proper fis- 

 sure in the anterior surface of the petrous bone and 

 under the entrance of the canal of Fallopius into 

 the petrous bone to join the facial. It is not always 

 present. 



passage in the bone, where it anastomoses with 

 the sympathetic nerve. The upper branch, the 

 continuation of the nerve, gives a twig to the 

 secondary membrana tympani. According to 

 Varrentrapp, there arises from it, by two roots, 

 a twig which runs on the inner wall of the 

 cavity of the tympanum, then into the Eusta- 

 chian tube, the cartilage of which it penetrates 

 anteriorly, and at last loses itself in the mucous 

 glands around its guttural orifice. A little 

 higher up a third branch goes to the vestibular 

 fenestra, and, according to Lauth, the tympanic 

 nerve receives, immediately on its entrance into 

 the canal in the upper part of the petrous bone, 

 a filament from the facial nerve. Moreover, 

 the tympanic nerve receives a filament of com- 

 munication from the external branch of the 

 nervus caroticus, the anterior and stronger 

 branch of the first cervical ganglion of the sym- 

 pathetic. 



From the otic ganglion a nerve goes to the 

 internal muscle of the malleus, ramus ad ten- 

 sorem tympani. It arises from the upper and 

 posterior part of the ganglion, and runs back- 

 wards on the inner side of the middle menin- 

 geal artery to the muscle. 



2. Nerves of the auricle and auditory pas- 

 sage. The auricle and auditory passage derive 

 their nerves from the cervical plexus, from the 

 facial, from the third branch of the fifth pair, 

 and also from the pneumogastric. 



The nerve from the cervical plexus is the 

 great auricular nerve, nervus auricularis mag- 

 nus. It comes off from the anterior branch of 

 the third cervical nerve, and is distributed 

 principally to the skin on the back of the 

 auricle and to the posterior muscles. One 

 branch passes between the antitragus and the 

 tail-like process of the helix to the other surface 

 of the ear and ramifies there. 



The facial nerve on its exit from the stylo- 

 mastoid hole gives off the posterior, inferior or 

 deep auricular nerve, nervus auricularis pos- 

 terior, profundus inferior, which receives a 

 twig from the pneumogastric and another from 

 the great auricular branch of the third cervical 

 and then divides into two branches, a posterior 

 larger, and an anterior smaller. The former 

 gives twigs to the skin of the mastoid process 

 and the retrahentes auriculam muscles, the 

 latter spreads on the lower and posterior part 

 of the cartilaginous auditory passage and the 

 concha, giving twigs to the skin of these parts 

 and the retrahentes auriculam. It sometimes 

 sends a branch through the cartilage into the 

 auditory passage to ramify in the integument 

 lining that part. 



The temporal branches of the facial nerve 

 send filaments to the skin of the anterior part 

 of the auricle, and to its anterior and superior 

 muscles. 



The superficial temporal nerve, a branch of 

 the posterior and inferior fasciculus of the third 

 division of the fifth pair, gives off two branches, 

 nervi meatus audUorii externi, inferior et supe- 

 rior, the ramifications of which are distributed 

 to the integument of the auditory passage and 

 concha. There is one branch, nervus tympani, 

 which runs under the upper wall of the osseous 



