55i 



THE CEANIAL XERVES. 



EIGHTH PAIR OF NERVES. 

 The eighth pair is composed of three distinct nerves — the glosso- 

 pharyngeal, pneumo-gastric, and spinal accessory, which leave the skull 

 through the anterior and inner division of the foramen lacerum posti- 

 cum, to the inner side and in front of the internal jugular vein. Two 

 of these nerves, the glosso-pharyngeal and pneumo-gastric, are attached 

 to the medulla oblongata in the same line, and resemble one another 

 somewhat in their distribution, for both are distributed to the first part 

 of the alimentaiy canal. The other, the spinal accessory, takes its 

 origin chiefly from the spinal cord, and is mainly distributed to muscles ; 

 but it gives fibres to the first two nerves by its communicating branch. 



I.— GLOSSO-PHARYNGEAL NERVE. 



The glosso-pharyngeal nerve is destined, as the name implies, for the 

 tongue and pharynx. 



Surface attachment. — The nerve arises from the surface of the 

 restiform body of the medulla by five or six roots, arranged in a vertical 

 line, the highest being contiguous to the facial and auditory nerves, the 

 lowest to the highest roots of the pneumogastric. 



Deep origin. — The fibres pass inwards and backwards through the 

 substance of the medulla, to reach the nucleus, a small column of large 

 nerve-cells placed deeply beneath the lower part of the floor of tlie 

 fourth ventricle, between the highest part of the vagal nucleus and the 

 lower part of the inner auditory nucleus. 



Fis. 345. 



Fig. 345. — Diagrammatic Sketch 

 from behind of the koots of the 

 Nerves of the Eighth Pair, with 

 THEIR Ganglia and CoiiiiUNiCA- 

 TI0N3 (from Bendz). 



A, x^art of the cerebellum above the 

 fourth ventricle ; B, medulla oblon- 

 gata ; C, posterior columns of the spina! 

 cord ; 1, root of the glosso-2)haryngeal 

 nerve ; 2, roots of the pneumo-gastric ; 



3, 3, 3, roots of the spinal accessory, 

 the uppermost number indicating the 

 filaments intermediate between the 

 spinal accessory and pneumo-gastric ; 



4, jugular ganglion of the glosso-pha- 

 ryngeal ; 5, petrous ganglion ; 6, 

 tympanic branch ; 7, ganglion of the 

 root of the x^neumo-gastric ; 8, auri- 

 cular branch ; 9, long ganglion on the 

 trunk of the X'^ieumo-gastric : 10, 

 branch from the ui^x^er ganglion to the 

 petrous ganglion of the glosso-x)haryn- 

 geal ; 11, inner portion of the spinal 

 accessory ; 12, outer x^ortion ; 13, 

 pharyngeal branch of the pneumo- 

 gastric ; 14, superior laryngeal 



branch ; 15, twigs connected with the sympathetic ; 16, fasciculus of the spinal accessory 

 l^rolonged with the pneumo-gastric. 



Course and distribution. — Directed outwards from its place of 

 origin over the flocculus to the foramen jugulare, it leaves the skull 

 with the pneumo-gastric and spinal accessory nerves, but in a separate 

 tube of dura mater. In passing through the foramen, somewhat in 



