PNEUMOGASTR1C NERVE. 113 



When the nerve has left the foramen, it receives the small part of the 

 spinal accessory, and swells into a ganglion nearly an inch long (gang, of 

 the trunk). Here the nerve lies between the internal carotid artery and 

 jugular vein, and communicates with several nerves. To reach the thorax, 

 the vagus descends almost vertically (fig. 25, 3 ) between the internal jugu- 

 lar vein and the internal and common carotid arteries; and enters that 

 cavity, on the right side, by crossing over the subclavian artery, but 

 beneath the innominate vein. 



* Ganglia. The ganglion of the root (gang, superius), (fig. 26, 8 ) is of 

 a grayish color, and in texture is like the ganglion on the large root of the 

 fifth nerve. Small branches in the foramen jugulare come from this gan- 

 glion. The ganglion of the trunk (gang, inferius), ( 9 ) is cylindrical in 

 form, is reddish in color, and is nearly an inch in length; it communicates 

 with the hypoglossal, spinal, and sympathetic nerves. All the intrinsic 

 fibres of the trunk of the nerve are surrounded by the ganglionic substance, 

 but those derived from the spinal accessory nerve ( n ) pass over the gan- 

 glion without being inclosed in it. 



The branches of the pneumogastric nerve may be arranged into those 

 uniting it with other nerves, and those distributed to parts around. 



* Connecting branches (fig. 26) arise from the ganglion of the root and 

 the ganglion of the trunk of the vagus. 



* From the ganglion of the root. The auricular branch ( 7 ) is the chief 

 offset, and crosses the jugular fossa to enter an aperture near the root of 

 the styloid process ; it traverses the substance of the temporal bone, and 

 reaches the outer ear, on which it is distributed. Its farther course will 

 be described with the anatomy of the ear. 



* One or two short filaments unite this ganglion with the spinal acces- 

 sory nerve ; and a branch of the sympathetic nerve in the neck enters it. 

 Occasionally there is an offset ( 10 ) to join the lower (petrosal) ganglion of 

 the glosso-pharyngeal nerve. 



From the ganglion of the trunk. Communicating filaments connect it 

 with the hypoglossal nerve. Other branches pass between it and the 

 upper ganglion of the sympathetic, and between it and the loop of the first 

 two cervical nerves. 



Branches for Distribution (fig. 25). The cervical branches arise from 

 the inner side of the nerve, and are directed inwards, to supply the 

 pharynx, the larynx, and the heart. 



a. The pharyngeal branch (fig. 26, 13 ) is an offset from the upper part 

 of the ganglion of the trunk, and terminates in the pharynx. The nerve 

 is directed inwards over the internal carotid artery (fig. 25, 5 ), and joins 

 the branches of the glosso-pharyngeal nerve on that vessel. Finally it 

 courses to the side of the middle constrictor muscle, and communicates 

 with branches of the glosso-pharyngeal. superior laryngeal, and sympa- 

 thetic nerves, to form the pharyngeal plexus. From the plexus branches 

 are furnished to the constrictors and palato-glossus and pharyngeus, and 

 to the pharyngeal mucous membrane between the tongue and the hyoid 

 bone. 



b. The superior laryngeal nerve (fig. 26, u ) is much larger than the 

 preceding branch, and comes from the middle of the ganglion of the trunk. 

 From this point it inclines obliquely inwards beneath the internal carotid 

 artery (fig. 25, 6 ), and reaches the larynx opposite the interval between 

 the hyoid bone and the thyroid cartilage. The nerve then perforates the 

 thyro-hyoid membrane, and is distributed to the mucous lining of the 



8 



