PNEUiMOGASTRIC NERVE. 405 



The Muscular branch divides into filaments, which are distributed to 

 the stylo-pharyngeus and to the posterior belly of the digastricus and 

 stylo-hyoideus muscle. 



The Pharyngeal branches are two or three filaments which are distri- 

 buted to the pharynx and unite with the pharyngeal branches of the pneu- 

 mogastric and sympathetic nerve to form the pharyngeal plexus. 



The Lingual branches enter the substance of the tongue beneath the 

 hyo-glossus and stylo-glossus muscle, and are distributed to the mucous 

 membrane of the side and base of the tongue, and to the epiglottis and 

 fauces. 



The Tonsillitic branches proceed from the glosso-pharyngeal nerve near 

 its termination ; they form a plexus (circulus tonsillaris) around the base 

 of the tonsil, from which numerous filaments are given off to the mucous 

 membrane of the fauces and soft palate, communicating with the posterior 

 palatine branches of Meckel's ganglion. 



PNEUMOGASTRIC NERVE (vagus). The pneumogastric nerve arises by 

 ten or fifteen filaments from the groove between the corpus olivare and 

 corpus restiforme, immediately below the glosso-pharyngeal, and passes 

 out of the skull through the inner extremity of the jugular foramen in a 

 distinct canal of the dura mater. While situated in this canal it presents 

 a small rounded ganglion (ganglion jugulare) ; and having escaped from 

 the skuh 1 , a gangliform swelling (plexus gangliformis), nearly an inch in 

 length, and surrounded by an irregular plexus of white nerves, which 

 communicate with each other, with the other divisions of the eighth pair, 

 and with the trunk of the pneumogastric below the ganglion. The plexus 

 gangliformis (ganglion of the superior laryngeal branch, of Sir Astley 

 Cooper,) is situated, at first, behind the internal carotid artery, and then 

 between that vessel and the internal jugular vein. The pneumogastric 

 nerve then descends the neck within the sheath of the carotid vessels, 

 lying behind and between the artery and vein, to the root of the neck. 

 Here the course of the nerve at opposite sides becomes different. 



On the right side it passes between the subclavian artery and vein to 

 the posterior mediastinum, then behind the root of the lung to the oeso- 

 phagus, which it accompanies to the stomach, lying on its posterior 

 aspect. 



On the left it enters the chest parallel with the left subclavian artery, 

 crosses the arch of the aorta, and descends behind the root of the lung, 

 and along the anterior surface of the oesophagus, to the stomach. 



The fibres of origin of the pneumogastric nerve, like those of the glosso- 

 haryngeal, may be traced through the fasciculi of the corpus restiforme 

 nto the grey substance of the floor of the fourth ventricle. 



The Branches of the pneumogastric nerve are the following : 

 Communicating branches with the Facial, 



Glosso-pharyngeal, 



Spinal accessory, 



Hypo-glossal, 



Sympathetic. 

 Auricular, 

 Pharyngeal, 

 Superior laryngeal, 



