618 THE CRANIAL NERVES. 



The muscular branches are given to the stylo-pharyngeus and constrictor 

 muscles. 



Tonsilitic brandies. When the glosso-pharyngeal nerve is near the tonsil, some 

 branches are distributed on that body in a kind of plexus (circulus tonsillaris). From 

 these nerves offsets are sent to the soft palate and the isthmus of the fauces. 



Lingual branches. The glosso-pharyngeal nerve divides into two parts at the 

 border of the tongue. One turns to the upper surface of the tongue, supplying the 

 mucous membrane at its base ; the other perforates the muscular structure, and ends 

 in the mucous membrane on the lateral part of the tongue. Some filaments enter 

 the circumvallate papillae. 



Summary. The glosso-pharyngeal nerve distributes branches to the 

 mucous membrane of the tongue, pharynx, tympanum, and Eustachian tube. 

 The muscles supplied by it are some of those of the pharynx and base of the 

 tongue. It is connected with the following nerves, viz., the lower maxillary 

 division of the fifth, the facial, the pneumo-gastric (the trunk and branches 

 of this nerve), and the sympathetic. 



PNEUMO-GASTRIC NERVE. 



The pneumo-gastric nerve (nervus vagus, par vagum) has the longest 

 course of any of the cranial nerves. It extends through the neck and the 

 cavity of the chest to the upper part of the abdomen ; and it supplies nerves 

 to the organs of voice and respiration, to the alimentary canal as far as the 

 stomach, and to the heart. 



The filaments by which this nerve springs from the medulla oblongata 

 are arranged in a flat fasciculus, immediately beneath the glosso-pharyngeal 

 nerve, and directed outwards with that nerve, across the flocculus to the 

 jugular foramen. 



In passing through the opening at the base of the skull the pneumo- 

 gastric nerve is contained in the same sheath of dura mater, and surrounded 

 by the same tube of arachnoid membrane as the spinal-accessory nerve ; but 

 it is separated from the glosso-pharyngeal nerve by a process of membrane. 

 In the foramen the filaments of the nerve become aggregated together ; and 

 it here presents a ganglionic enlargement, distinguished as the ganglion of 

 the root of the pneumo-gastric. After its passage through the foramen, it 

 is joined by the accessory part of the spinal accessory nerve, and a second 

 ganglion is formed upon it, the ganglion of the trunk of the nerve. Several 

 communications are at the same time established with the surrounding 

 nerves. 



The upper ganglion, or ganglion of the root of the pneumo-gastric nerve, 

 situated in the foramen jugulare, is of a greyish colour, nearly spherical, and 

 about two lines in diameter ; it has filaments connecting it with other nerve*, 

 viz., with the facial, the petrous ganglion of the glosso-pharyngeal, the 

 spinal accessory, and the sympathetic. 



The lower ganglion, or ganglion of the trunk or the pneumo-gastric nerve, 

 is about half an inch below the preceding. Occupying the trunk of the 

 nerve outside the skull, it is of a flattened cylindrical form and reddish 

 colour, and measures about ten lines in length and two in breadth. The 

 ganglion does not include all the fibres of the nerve; the fasciculus, which 

 is sent from the spinal accessory to join the vagus, is the part not in- 

 volved in the ganglionic substance. It communicates with the hypoglossal, 

 the spinal, and the sympathetic nerves. 



The pneumo-gastric nerve descends in the neck, between and concealed 



