ROOTS OF THE CRANIAL NERVES. 687 



Kolliker concurs, state that the fibres may be traced more deeply to the 

 floor of the fourth ventricle. 



7. The seventh pair of nerves appear on each side at the posterior margin 

 of the pons, between the middle and inferior peduncles of the cerebellum, 

 and nearly in a line with the place of attachment of the fifth nerve. 



Deep origins. The portio dura or facial nerve, placed a little nearer to the middle 

 line than the portio mollis, may be traced to the medulla oblongata between the resti- 

 form and olivary fasciculi, with both of which it is said to be connected. Some of its 

 fibres are derived from the pons. Philipeaux and Vulpian affirm that the fibres arise 

 from the outer wall of the fourth ventricle, and that many of them decussate in its 

 floor. 



Connected with the portio dura, and intermediate between it and the portio 

 mollis, is a smaller white funiculus, first described by Wrisberg (portio inter duram et 

 mollein). The roots of this accessory or intermediate portion are connected deeply 

 with the lateral column of the cord. 



The portio mollis, or auditory nerve, rises from the floor of the fourth ventricle, at 

 the back of the medulla oblongata, in which situation, as already described, trans- 

 verse white striae are seen, which form the commencement of the nerve. These 

 roots are connected with the grey matter, and some appear to come out of the median 

 fissure. The nerve then turns round the restiform body, and becomes applied to the 

 lower border of the pons, receiving accessions from the former of those parts, and 

 according to some authors from the latter also. 



Eoville says that the roots of the portio mollis are also connected by a thin layer 

 on the under surface of the middle peduncle with the cortical substance of the cere- 

 bellum ; also, with the small lobule named the flocculus ; and with the grey matter at 

 the borders of the calamus scriptorius. 



8. The eighth nerve consists of three distinct portions. 



The uppermost portion is the glosso-pharyngeal nerve ; next to this, and 

 lower down, is the par vagum or pneumo-gastric nerve consisting of a larger 

 number of cords. The roots of both these nerves are attached superficially 

 to the fore part of the restiform. body. Still lower, is the spinal accessory 

 nerve, which, ascending from the side of the spinal cord, enters the skull by 

 the foramen magnum, and is associated with the pneumo-gastric nerve as it 

 passes out through the foramen lacerum. 



The accessory nerve arises within the spinal canal from the lateral 

 column of the cord behind its middle, by a series of slender roots, which 

 commence as low down as the fifth or sixth cervical nerve. The nerve 

 passes upwards between the posterior roots of the cervical nerves and the 

 ligamentum deiiticulatuin, the several funiculi of origin successively joining 

 it as it ascends. On entering the skull, it receives funiculi from the side 

 of the medulla oblongata. 



These three portions of the eighth pair are connected deeply with grey nuclei 

 within the cord and medulla oblongata, as already described (see p. 521 ). 



9. The ninth nerve (hypoglossal) arises, in a line continuous with that 

 of the anterior roots of the spinal nerves, by scattered funiculi from the 

 furrow between the olivary body and the anterior pyramid. 



The roots of the ninth nerve are traced by Stilling to one of the grey nuclei already 

 described in the medulla oblongata, and they are said by Kolliker to undergo partial 

 decussation in the floor of the fourth ventricle. 



DISTRIBUTION OF THE CRANIAL NERVES. 



Mode of exit from the cranium. Each of the cranial nerves issues at 

 first from the cranial cavity through a foramen or tubular prolongation of 

 the dura mater : some of these nerves or their main divisions are contained 



Q Q 2 



