THE GLOSSOPHARYNGEAL KERVE. 261 



artery and unites with the pharyngeal branch of the vagus to form the pharyngeal 

 plexus (p. 2C5) ; this branch is sometimes divided into two or even three parts. 

 One or two smaller twigs pass inwards through the superior constrictor muscle, and 

 supply the mucous membrane of the upper part of the pharynx. 



A muscular branch is furnished to the stylo-pharyngeus, and sends also fila- 

 ments through the muscle to the mucous membrane of the pharynx. 



Tonsillitic branches. Slender filaments pass from the glosso -pharyngeal 

 nerve, as it approaches the base of the tongue, to the tonsil, over which they form 

 a sort of plexus (circulus tonsillaris), to the soft palate, and to the pillars of the 

 fauces. 



Lingual branches. The glosso-pharyngeal nerve divides as it passes beneath 

 the hyo-glossus muscle into two parts. One turns to the upper surface of the tongue 

 and subdivides into many branches, which supply the circumvallate papillae and the 

 mucous membrane over the posterior third of the organ, the hindmost filaments 

 reaching the anterior surface of the epiglottis. The other is smaller, and is distri- 

 buted to the mucous membrane of the side of the tongue, extending to about the 

 middle of its length, where it forms a communication with the lingual nerve. 

 Beneath the mucous membrane the terminal filaments are united in a plexus which 

 contains microscopic ganglia. 



Variety. In one case a branch from the glosso-pharyngeal supplied the mylo-hyoid 

 muscle and the anterior belly of the digastric, the normal mylo-hyoid nerve being wanting 

 (Guy's Hosp. Reports, vol. xiv, p. 453). 



SUMMARY. The glosso-pharyngeal nerve distributes branches to the mucous 

 membrane of the tongue, pharynx and middle ear, as well as to the stylo-pharyngeus 

 muscle, and possibly also to the middle constrictor of the pharynx. By its small 

 superficial petrosal branch it furnishes secretory and vaso-dilator fibres (through 

 the otic ganglion and the auriculo-temporal nerve) to the parotid gland. It is 

 connected with the following nerves, viz., the inferior maxillary division of the fifth 

 (through the otic ganglion), the facial, the pneumo-gastric (its trunk and branches), 

 and the sympathetic. 



X. PNEUMO-GASTRIC NERVE. 



The tenth or pneumo-gastric nerve (nervus vagus, par vagum) is much larger 

 than the glosso-pharyngeal, and has the longest course of all the cranial nerves, 

 extending through the neck and thorax to the upper part of the abdomen. It arises 

 from the medulla oblongata immediately in front of the restiform body, by twelve or 

 fifteen filaments beginning close below, and continuing the line of, the roots of the 

 glosso-pharyngeal nerve. Its central connections are similar to those of the glosso- 

 pharyngeal, the roots passing backwards towards the floor of the fourth ventricle, 

 where the greater part of the fibres enter the vagal nucleus beneath the ala cinerea, 

 while a smaller number pass into the funiculus solitarius, and a third set, believed to 

 be efferent, spring from the accessory vagal nucleus. 



The fibres of the vagal roots are mostly small. In the trunk of the nerve there are 

 also numerous fibres of medium size, but these are probably derived in large part from the 

 bulbar portion of the spinal accessory nerve, which joins the vagus close below the skull. 

 Many of the larger fibres are continued into the pharyngeal and inferior laryngeal branches, 

 which are in great measure distributed to striped muscles. 



The roots of the vagus form at first a flat band, which is directed outwards 

 below the flocculus to the middle compartment of the jugular foramen. Here the 

 nerve is contained in the same sheath of dura mater and arachnoid as the spinal 



