ORIGIN OF THE CR AXIAL XERVES. 720 



///. The large root divides within the pons into two parts. One Deep origin 

 of these is connected with a mass of grey matter (sensory nucleus of the fifth) pf large root 

 near the floor of the fourth ventricle : the other (ascending root of the fifth ; InediiuV 1 

 fig. _'i7 Va. p. 739) arises from the cells of the posterior horn of the grey matter oblongata ; 

 in the lower part of the medulla oblongata and upper part of the spinal cord, 

 an- 1 is directed upwards on the outer surface of the gelatinous substance of 

 Rolando to join the upper part. 



The xinaU root also has a double origin, one part springing from a special of smalljn 

 nucleus motor nucleus of the fifth) in the floor of the fourth ventricle internal 

 to the sensory nucleus, and the other (descending root of the fifth ; fig. 283, 

 p. 775) from a collection of nerve-cells on the side of the aqueduct of Sylvius. 



The SIXTH NERVE ( 6 ), abducent nerve of the eyeball comes through Sixth nerve 

 the outer part of the anterior pyramid close behind the pons, and 

 often by a second band from the lower border of the pons. 



Deep oriyin. The fibres of the nerve pass forwards, through the lower and nucleus 

 part of the pons, from a nucleus in the floor of the fourth ventricle, beneath beneath 

 the outer part of the fasciculus teres (fig. 267). ventricle. 



The SEVENTH or FACIAL NERVE (?) appears at the lower border of seventh 

 the pons, to which it is closely adherent, in the depression between J^ra/tract 

 the upper ends of the olivary and restiform bodies. A small accessory ? f . b "J b: 

 bundle (jiortio ini- rin<-<li<'i. of Wrisberg) leaves the medulla oblongata intermediate 

 1 jet ween the facial and the auditory nerves, and joins the former P 01 ^ 011 - 

 within the internal auditory meatus. 



Deep origin. The fibres of the facial nerve pass backwards to the floor of Deep origin 

 the fourth ventricle, and there wind round the nucleus of the sixth nerve, to fro m a 

 arise from a group of nerve-cells lying in front and to the outer side of the ^^"part 

 latter (fig. 267). Whether some of the fibres are connected with the cells of of pons. 

 the nucleus of the sixth is uncertain. 



The EIGHTH or AUDITORY NERVE has a surface attachment outside Eighth 

 the foregoing to the restiform body internal to the flocculus ; one of 

 its roots passing round the restiform body to its dorsal surface. body- 



riijin. At its attachment to the medulla oblongata, the auditory Deep origin, 

 nerve consists of two roots, upper and lower. The fibres of the upper or 

 dorsal part constitute the cochlear division of the nerve, some of its fibres Cochlear 

 terminate in cells forming the ventral cochlear nucleus on the under part of division, 

 the restiform body, and others pass to the dorsal cochlear nucleus (outer 

 auditory nucleus) in the lateral angle of the floor of the fourth ventricle 

 dorsal to the restiform body. The fibres of the striae acusticae arise from the 

 latter nucleus, and they, with many more from the ventral nucleus, eventually 

 pa.ss. through the intervention of the superior olivary nucleus and other groups 

 of cells, into the lateral fillet and are connected with the posterior corpus 

 quadrigeminum. 



The lower, or ventral part of the auditory nerve constitutes the vestibular Vestibular 



,'. -Many of its fibres pass through the pons, internal to the restiform division. 

 body to the inner auditory nucleus, or the dorsal vestibular nucleus, beneath 

 the auditory tubercle in the floor of the fourth ventricle : other fibres pass to 

 groups of large cells internal to and beneath, the restiform body forming the 

 nucleus of Deiters, and some to a group of cells styled the nucleus of the 

 descending root. Many fibres from the dorsal nucleus of the vestibular 

 division of the auditory nerve pass through the restiform body into the 

 cerebellum. 



The NINTH or GLOSSO-PHARYNGEAL NERVE ( 8 ) leaves the medulla Ninth nerve 



below facial 



