270 THE CRANIAL NERVES. 



medulla oblongata below the pneumo-gastric nerve, and from the lateral column of 

 the spinal cord as low down as the fifth or sixth cervical nerve. The filaments 

 arising from the medulla oblongata form the small bulbar portion of the nerve. The 

 lowest spinal filaments are attached to the middle of the lateral column ; the highest 

 ones arise close to the posterior nerve-roots, with the upper one or two of which they 

 are frequently connected. 



According to Holl the association of the dorsal root of the first cervical nerve with the 

 spinal accessory is only apparent, the two being merely bound together by connective tissue, 

 and not interchanging any fibres. Kazzander found, however, in many cases a common 

 origin of rootlets of the accessory and first cervical nerves, or a passage of filaments between 

 the two, and less frequently a communication with the second cervical nerve. In one case 

 also there was a small ganglion on the highest root of the bulbar portion of the spinal acces- 

 sory nerve. (M. Holl, "Ueb. d. Nerv. accessorius Willisii." Arch. f. Anat., 1878; J. Kaz- 

 zander. " Ueb. d. N. accessorius Willisii u. seine Beziehungen zu d. oberen Cervicalnerven," &c. r 

 Arch. f. Anat., 1891.) 



In the bulbar portion of the eleventh nerve fine fibres predominate, although there are some 

 of medium and large size. The spinal portion of the nerve consists almost wholly of large 

 fibres, and fine fibres are absent. 



The bulbar portion is directed outwards with the pneumo-gastric nerve : the 

 spinal part ascends between the ligamentum denticulatum and the posterior 



Fig. 182. SECTION OF' UPPER END OF SPINAL CORD, SHOWING ORIGIN 

 OF SPINAL ACCESSORY NERVE. (After Lockhart Clarke. ) 



/, anterior, fp, posterior median fissure ; p, end of decussation of 

 pyramids ; Cla, GIp, anterior and posterior roots of first cervical 

 nerve ; XI, root of spinal accessory nerve ; c, central canal. 



roots of the cervical nerves, passes into the skull 

 through the foramen magnum, and immediately bends 

 outwards to enter the middle compartment of the 

 jugular foramen, where the nerve is contained in the 

 same sheath of dura mater as the vagus (see Vol. II, fig. 182). In the foramen, 

 the two parts of the nerve interchange fibres, and they are sometimes intimately 

 united so as to form a single trunk for a short distance. The accessory part is 

 also connected by one or two filaments with the ganglion of the root of the pneumo- 

 gastric. 



Below the skull, the internal, bulbar, accessory or vagal portion passes 

 over the surface of the lower ganglion of the vagus, and sends its fibres into the 

 pharyngeal and superior laryngeal branches, and into the trunk of that nerve belcw 

 the ganglion in the manner already described. 



The bulbar portion of the spinal accessory nerve contains the inhibitory fibres which pass 

 by the vagus to the heart, and, as has been shown for the monkey by the experiments of Beevor 

 and Horsley and of Rethi, the motor fibres of the levator palati and azygos uvulae, as well as, 

 in part at least, of the constrictor muscles of the pharynx. It is generally stated also that the 

 motor fibres of the laryngeal muscles are derived from the same source, but this view is not 

 confirmed by recent observations of Grossmann, Gra bower and Navratil. (Beevor and 

 Horsley, "Note on some of the Motor Functions of certain Cranial Nerves (V., VII., IX., X., 

 XI., XII.), and of the three first Cervical Nerves, in the Monkey," Proc. Roy. Soc., 1888 ; 

 L. Rethi, "Die Nervenwurzeln der Rachen- und Gaumenmuskeln," and "Der periphere 

 Verlauf der motorischen Rachen- und Gaumennerven," Wiener Sitzungsber., 1892 and 1893 ; 

 M. Grossmann, " Ueber die Athembewegungen des Kehlkopfes, II. Die Wurzelfasern der 

 Kehlkopfn erven," Wiener Sitaungsber.. 1889 ; Grabower, "Das Wurzelgebiet der motorischen 

 Kehlkopfnerven," Centralbl. f. Physiol., iii, 1890; E. v. Navratil. ' Thierversuche iiber die 

 Kehlkopfinnervation und iibei den N. accessorius Willisii." Ungar. Arch. f. Med., ii, 1894.) 



