2QO THE NERVOUS SYSTEM 



Tenth Nerve (Pneumogastric, Vagus). 



Origin. This is a mixed nerve. Its apparent origin is from 

 the groove between the olivary and restiform bodies below the 

 ninth. Its deep origin is in the floor of the fourth ventricle 

 just below that of the glasso-pharyngeal. 



Course and Distribution. As it leaves the cranium by the 

 jugular foramen it presents a ganglionic enlargement, the jugu- 

 lar ganglion, or ganglion of the root, just below which it is 

 joined by the accessory portion of the spinal accessory. Below 

 the junction is a second ganglion, the ganglion of the trunk. 

 The accessory part of the eleventh passes through this ganglion, 

 and below unites with the vagus trunk to pass chiefly into its 

 pharyngeal and superior laryngeal branches. The pneumogas- 

 tric passes down the neck behind and between the internal jugu- 

 lar vein and the internal and common carotid arteries, and sends 

 motor and sensory fibers to the organs of voice and respiration, 

 and motor fibers to the pharynx, esophagus, stomach and heart. 



The branches of the pneumogastric are numerous, (i) In 

 the jugular fossa it gives off (a) ameningeal branch to the dura 

 mater of the posterior fossa of the skull ; (b) an auricular branch 

 which, traversing the substance of the temporal bone, emerges 

 by the auricular fissure to supply the integument of the back 

 part of the pinna and external auditory meatus. (2) In the 

 neck it gives off (a) a pharyngeal branch, which consists mainly 

 of fibers from the accessory portion of the eleventh and is the 

 chief motor nerve of the pharynx and soft palate; (b) a superior 

 laryngeal branch, which also consists mainly of fibers from the 

 accessory part of the eleventh and is the chief sensory nerve 

 of the larynx; it also animates the crico-thyroid muscle; (c) a 

 recurrent laryngeal branch, which, on the right side, winds 

 round the subclavian artery, and, on the left, round the aorta to 

 return to the muscles of the larynx whose motor nerve it is; (d) 

 cervical cardiac branches, which communicate with the cardiac 



