PNEUMOGASTRIC NERVE. 499 



which they pass, and go to their several destinations. In 

 the foramen lacerum, the par vagum is separated from the 

 other nerves by dense cellular membrane, and from the 

 jugular vein, which is behind, by a spicula of bone. At 

 this point it also presents a swelling called the superior 

 ganglion, and below this another enlargement called the 

 inferior gangli6n, about an inch in length. From these, 

 filaments communicate with the facial, spinal accessory, 

 glosso-pharyngeal, sympathetic, and superior spinal nerves, 

 constituting a plexus termed the basilar plexus. From the 

 inferior ganglion, which is of reddish color, the par vagum 

 descends the forepart of the neck, along with the carotid 

 artery and jugular vein, behind and between those vessels, 

 and enclosed in the same sheath with them. At the root 

 of the neck, the right par vagum enters the chest between 

 the subclavian vein and artery, crossing the latter at right 

 angles ; on the left, this nerve runs parallel to the sub- 

 clavian artery, crossing the arch of the aorta. Both nerves 

 now proceed through the thorax to the posterior part of the 

 root of the lungs, in the posterior mediastinum, and descend 

 along the oesophagus, through the diaphtagni, to terminate 

 upon the stomach. 



The par vagum in its course gives off the following 

 branches : 



The auricular commences at the superior ganglion, con- 

 nects with the glosso-pharyngeal, enters a small canal of 

 the petrous bone, upon the inside of the styloid process, 

 then proceeds to join the facial in the aqueduct of Fallo- 

 pius, and finally escapes in front of the mastoid process to 

 supply the ear and its integuments. 



The pliaryngeal comes from the inferior ganglion at the 

 base of the cranium, receives a branch from the spinal acces- 

 sory, and descends behind the carotid artery to the side of 

 the pharynx, at the upper margin of its middle constrictor. 

 Here it anastomoses with branches from the glosso-pharyn- 

 geal, the superior laryngeal, and the sympathetic, forming 

 the pharyngeal plexus , which supplies the mucous and mus- 

 cular structures of the pharynx. 



