274 



THE CAT. 



[CHAP. ix. 



The SEVENTH, or FACIAL nerve (called also the portio dura, when 

 reckoned as one with the auditory nerve) has its deep origin in the 

 medulla oblongata between the restiform and olivary bodies, and 

 perhaps from the outer wall of the fourth ventricle. 



It com.es to the surface from the corpus trapezoideum (Fig. 128, 

 VII.} just outside and slightly behind the origin of the sixth nerve. 

 Entering the meatus auditorius internus, it proceeds through the 

 aqueduct of Fallopius, and emerging at the stylo-mastoid foramen 

 (Fig. 130, 7 ), penetrates the parotid gland, when it divides (behind 

 the mandible) into two branches, the subdivisions of which ramify 

 over the side of the head, face and neck, going to the muscles 

 of the ear, scalp, mouth, nose, and eyelids, and also to the platysma 

 myoides (Fig. 88, n). 



Near its exit from the aqueduct it gives off a slender branch, 

 called the chorda tympani, which enters the hinder part of the 

 tympanic cavity (by a canal opening close to the bony frame of the 

 tympanic membrane), crosses that membrane and that process of 

 the malleus which is called the manubrium,* and finally escapes 

 through the fissura Glaseri to join the gustatory nerve as already 

 mentioned. 



14. The EIGHTH, or AUDITORY nerve (called also the portio mollis, 

 when reckoned as one with the auditory nerve), has its deep origin in 

 the floor of the fourth ventricle. It also receives accessions by fibres 

 from the restiform body and, perhaps, also from the pons. It emerges 

 from the surface of the encephalon behind the pons, from the corpus 

 trapezoideum (Fig. 128, VIII.), just behind and external to the 

 emergence of the seventh nerve. It enters the meatus auditorius 

 internus along with the seventh nerve, and bifurcates at the end of 

 that canal, one part going through the anterior part of the cribriform 

 lamina to the cochlea and the other through its hinder part to the 

 vestibule, as described in treating of the organ of hearing. 



15. The NINTH, or GLOSSO-PHARYNGEAL nerve (Figs. 128, IX., and 

 130, 9 ), has its deep origin in the grey matter of the posterior part 

 of the medulla oblongata. It quits the surface of the encephalon 

 just behind (and below) the origin of the seventh nerve, emerging 

 behind the upper part of the olivary body and superficially connected 

 with the restiform body. It quits the skull by the jugular foramen, 

 and then descends between the carotid artery and the jugular vein, 

 but turns forwards and inwards at the lower border of the stylo- 

 pharyngeus muscle, and goes to the tongue, passing under the 

 hyoglossus muscle and being distributed to that organ and to the 

 tonsil and pharynx. 



The TENTH, or PNEUMOGASTRIC nerve (Figs. 128, X., and 130, 10 ), 

 called also the PAR VAGUM, is the longest of all the nerves of the 

 encephalon, extending downwards as far as the stomach. Its deep 

 origin is situated in the grey nuclei of the hinder part of the medulla 



* For the explanation of these terms, see the description of the internal ear, 

 infra, p. 298. 



