THE TENTH, VAGUS, OR PNEUMOGASTRIC NERVE 687 



ganglion and passes upward between the petrous and tympanic parts of the temporal 

 bone to reach the cavity of the tympanum. Here it breaks up into branches 

 to form, along with branches from the carotid plexus of the sympathetic, the tym- 

 panic plexus. From the ])lexus branches pass to the mucous memljrane of the 

 tympanum and the Eustachian tube. The continuation of the nerve issues from 

 the plexus and unites with a filament from the geniculate ganglion of the facial to 

 form the small superficial petrosal nerve; this runs forward and ends in the otic 

 ganglion. 



Filaments also connect the petrous ganglion with the jugular ganglion of the vagus nerve 

 and with the superior cervical ganglion of the sj'mpathetic. 



2. A considerable branch runs backward on the guttural pouch, contributes 

 filaments to the pharyngeal plexus, and concurs with twigs from the vagus and the 

 sympathetic in forming the carotid plexus on the terminal part of the carotid 

 artery and on its chief ]:)ranches. In this plexus is the small ganglion intercaroticum. 



The pharyngeal branch (R. pharyngeus) (Fig. 437) is the smaller of the two 

 terminal branches. It runs forward across the deep face of the great cornu of the 

 hyoid bone and concurs with the pharyngeal branches of the vagus and with sym- 

 pathetic filaments in forming the pharyngeal plexus; from this branches pass to 

 the muscles and mucous membrane of the pharynx. 



The lingual branch (R. lingualis) is the continuation of the trunk (Fig. 437). 

 It runs along the posterior border of the great cornu of the hyoid bone in front of 

 the external maxillary artery and dips under the hyo-glossus muscle. It gives 

 collateral branches to the soft palate, isthmus faucium, and tonsil, and ends in 

 the mucous membrane of the posterior part of the tongue, where it supplies gusta- 

 tory fibers to the vallate papillae. A considerable branch unites with a twig from 

 the lingual nerve. 



The glosso-pharyngeal is a mixed nerve, containing both motor and sensory fibers. The 

 latter constitute the bulk of the nerve anfl include those which mediate the special sense of taste. 

 They are processes of the cells of the petrous ganglion. The central processes of the ganglion 

 cells enter the medulla, pass upward and inward through the formatio reticularis, and end in the 

 nucleus of termination in the floor of the fourth ventricle. The motor fibers arise from dorsal 

 and ventral efferent nuclei in the medulla. The glosso-pharyngeal shares these nuclei with the 

 vagus and has practically the same central connections as that nerve (q. v.). 



THE TENTH, VAGUS, OR PNEUMOGASTRIC NERVE 



The vagus or pneumogastric (N. vagus) is the longest and most widely dis- 

 tributed of the cranial nerves; it is also remarkable for the connections which it 

 forms with adjacent nerves and with the sympathetic. It is attached to the lateral 

 aspect of the medulla by several filaments which are in series with those of the 

 ninth nerve in front and the eleventh nerve behind (Fig. 499). The bundles con- 

 verge to form a trunk which passes outward, pierces the dura mater, and emerges 

 from the cranium through the foramen lacerum posterius (Fig. 515). In the 

 foramen the nerve bears on its lateral aspect the elongated flattened jugular gang- 

 lion (G. jugulare). 



The ganglion communicates with (a) the tympanic nerve, (b) the petrous ganglion of the 

 ninth nerve, (c) the spinal accessory, and (d) the hypoglossal. It also gives off the auricular 

 branch (R. auricularis), which runs forward below the petrous ganglion and passes through a 

 small canal in the petrous temporal bone to gain the facial canal. Here it gives filaments to the 

 facial and emerges with that nerve through the stylo-mastoid foramen. It ascends behind the 

 external auditory meatus, dips under the rotator longus muscle, and passes through a foramen 

 in the conchal cartilage to ramify in the integument which lines the meatus and the adjacent 

 part of the ear. 



Beyond the ganglion the vagus runs backward and downward with the spinal 

 accessory in a fold of the guttural pouch (Fig. 437). Then the two nerves separate, 

 allowing the hypoglossal to pass between them, and the vagus descends with the 



