THE AUDITORY NEEVE. 553 



scalp ; to those of the mouth, nose, and eyelids ; and to the cutaneous 

 muscle of the neck (platysma). It likewise supplies branches to the 

 integument of the ear, to that of the side and back of the head, as well 

 as to that of the face and the upper part of the neck. 



This nerve is connected freely with the three divisions of the fifth 

 nerve, and with tiie submaxillary and spheno-palatine ganglia ; with 

 the glosso-pharyngeal and pneumo-gastric nerves : with the auditory, 

 and with parts of the sympathetic and the spinal nerves. 



Varieties. — The chorda, tympani has been found more or less separate from 

 the trunk of the lingual nerve, and in these cases it is very easy to trace the 

 distribution of its terminal branches. Thus, in a case reported by Embleton 

 (JoiuTi. of Anat., vol. vi.. p. 217), the chorda applied itself to the inferior dental 

 nerve, which it only left a line or t-^\'o above the dental canal, and, passing on, 

 divided mto branches to the submaxillary and sublingual glands, and to the 

 lingual nerve. 



AUDI.ORY NEEVE. 



The auditory nerve, or portio mollis of the seventh pair, is the special 

 nerve of the organ of hearing, and is distributed exclusively to the 

 internal ear. 



Surface attachment. — The auditory nerves appear at the lower 

 border of the pons, on the outer side of and close to the facial nerves. 

 They are also connected with the lower edge of the pons opposite the 

 restiform body, from the inner side or middle of which they emerge. 



Deep origin. — The fibres of the nerve divide into two nearly equal 

 parts, of which one, posterior, winds round the restiform body, while 

 the other, anterior, passes through its substance. The chief nucleus of 

 the nerve (inner nucleus) forms a convex prominence in the outer 

 portion of the lower half of the floor of the fourth ventricle. Its 

 transverse section is triangular, and it is composed of small, round, 

 oval and triangular cells. The posterior portion of the auditory nerve, 

 winding round the restiform body (with which it is connected;, reaches 

 the outer part of this nucleus. The anterior division passes through the 

 substance of the inferior peduncle of the cerebellum towards the apes of 

 the inner nucleus. A few of its fibres join the inner nucleus ; the majority, 

 however, turn outwards to a network of cells and fibres in the posterior 

 portion of the restiform body (outer nucleus, Lockhart Clarke) to the 

 outer side of the inner nucleus. Some of the fibres of this division turn 

 outwards along the restiform body to reach the cerebellum, where they 

 have been traced to the superior vermiform process. Both portions of 

 the auditory nerve contain many nerve-cells : in the posterior portion 

 they constitute a pyriform swelling at the anterior edge of the restiform 

 body. 



Course. — As the auditory nerve is inclined outwards from its connec- 

 tion with the medulla oblongata to gain the internal auditory meatus, ic 

 is in contact with the facial nerve, being only separated from it in part 

 by a small artery destined for the internal ear. Within the meatus the 

 two nerves are connected to each other by one or two small filaments. 

 Finally the auditory nerve bifurcates in the meatus : one division, 

 piercing the anterior part of the cribriform lamina, is distributed to the 

 cochlea; the other, piercing the posterior half of the lamina, enters 

 the vestibule of the internal ear. The distribution of these branches 

 will be described with the ear. 



