THE HEAD AND NECK 1227 



canaliculus it traverses the petrous portion of the temporal bone, 

 crossing in its course the inner aspect of the descending portion of the 

 aqueduct of Fallopius a little above the stylo-mastoid foramen, where 

 it forms its first communication with the facial nerve. It then emerges 

 from the pars petrosa through the auricular or tjTnpano-mastoid 

 fissure, between the mastoid process and the tympanic plate, and 

 thereafter divides into two branches. One of these joins the 

 posterior auricular branch of the facial nerve, and the other is 

 distributed to (a) the skin of the inner surface of the auricle, and 

 (b) the skin of the lower and back part of the external auditory 

 meatus. 



B. Ganglion of the Trunk — i. Branches of Communication. — 

 (a) The most important branch of conmiunication is the bulbar 

 or accessory portion of the spinal accessory nerve, which passes over 

 the surface of the ganglion in intimate contact with it. Most of the 

 bulbar fibres are continued into the pharyngeal and superior laryn- 

 geal nerves, but some of them descend in the main trunk of the 

 pneumogastric, and pass into its cardiac and inferior laryngeal 

 branches. The bulbar fibres are to be regarded as of two kinds, 

 namely, motor, for the muscles of the soft palate, pharynx, and 

 larynx, and cardiac inhibitory, [b) Branches pass between the 

 ganglion of the tnink and the hypoglossal nerve, (c) A communi- 

 cating branch is received from the superior cervical ganglion of the 

 sympathetic. 



2. Branches of Distribution. — ^These are two in number, namely, 

 pharyngeal and superior laryngeal. 



The pharyngeal nerve arises from the upper part of the ganglion 

 of the trunk, its fibres being chiefly derived from the bulbar or acces- 

 sory portion of the spinal accessory nerve. It passes forwards 

 and downwards over the internal carotid artery, and divides into 

 branches opposite the middle constrictor muscle, which join the 

 pharyngeal branches of the glosso -pharyngeal and superior cervical 

 ganglion of the sympathetic to form the pharyngeal plexus. 



The pharyngeal plexus is situated upon the middle constrictor 

 muscle of the pharjmx. It is formed by (i) the pharyngeal branch 

 of the ganglion of the trunk of the pneumogastric ; (2) the pharyn- 

 geal branches of the glosso-pharyngeal ; and (3) the pharyngeal 

 branches of the superior cervical ganglion of the sympathetic. 



Branches. — ^These are distributed to (i) the constrictor muscles 

 of the pharynx ; (2) the mucous membrane of the pharynx ; and 

 (3) the palato-glossus, palato-pharyngeus, levator palati, and azj-gos 

 uvulae muscles. Branches of communication pass betu-een the 

 plexus and the superior laryngeal and external laryngeal nerves, 

 and another branch, known as the lingual branch of the vagus, 

 passes to the hypoglossal nerve. 



Superior Laryngeal Nerve. — This nerve, which is principally 

 sensory, arises from the ganglion of the trunk of the pneimiogastric 

 near its centre, and contains fibres of the bulbar or accessory 

 portion of the spinal accessory nerve. It passes downwards and 



