472 NERVOUS SYSTEM. 



muscles of the tongue, and others may be traced along the ex- 

 ternal margin of the tongue, beneath its mucous membrane for 

 some distance. Scarpa has delineated a remarkable plexus, 

 which he denominates Circulus Tonsillaris Anderschii or Anas- 

 tomosis Plexuosa, formed by these several filaments and by 

 branches of the lingual, on the side of the root of the tongue, 

 at the base of the tonsil gland. 



SECT. XI. NERVUS PNEUMOGASTRICUS. 



The Pneumogastric Nerve (Nervus Pneumogastricus, Vagus, 

 Par Octavum, Decimum of Andersach,) at its exit from the cra- 

 nium through the posterior foramen laeerum, in front of the in- 

 ternal jugular vein, is closely united to the hypo-glossal, glosso- 

 pharyngeal, and accessory nerves, by compact cellular substance. 

 It is first placed in front of the hypo-glossal nerve, but, in a short 

 space, gets behind it, and is also separated from the glosso-pha- 

 ryngeal by the internal jugular vein. Opposite the transverse 

 process of the atlas, it leaves the hypo-glossal nerve, and as- 

 sumes a position between the internal carotid and the internal 

 jugular, on the vertebral side of these vessels, and is enveloped 

 in their sheath of dense cellular substance. It maintains this 

 relative position along the common carotid to the root of the 

 neck. 



At the latter place, the pneumogastric of the right side goes 

 in front of the subclavian artery, Rear its root, but on the left 

 side it crosses the root of the left subclavian artery, and the arch 

 of the aorta to the left of the origin of the left carotid. In 

 getting fairly into the cavity of the thorax, it is directed back- 

 wards and downwards from these points towards the posterior 

 face, of the bronchus, between it and the pleui-a. It then aban- 

 dons the bronchus, and applies itself to the oesophagus, and fol- 

 lows it through the diaphragm to the stomach. The nerve of 

 the left side, in its course along the oesophagus, is on the front 

 surface of the latter, and the nerve of the right side, on its pos- 

 terior surface. 



The pneumogastric anastomoses with the accessory while 

 passing through the foramen laeerum posterius. Somewhat 

 lower down, it also anastomoses with the glosso-pharyngeal and 

 with the superior cervical ganglion of the sympathetic. The 



