PNEUMOGASTRIO, OR PAR VAGUM NERVE. 



645 



descend in the substance of the medulla. It is difficult to follow the fibres of origin of 

 the pneumogastrics beyond the median line ; but recent observations leave no doubt oi 

 the fact that many of these fibres decussate in the floor of the fourth ventricle. 



There are two ganglionic enlargements belonging to the pneumogastric. In the 

 jugular foramen, is a well-marked, grayish, ovoid enlargement, from one-sixth to oner 

 fourth of an inch in length, called the jugular ganglion, or the ganglion of the root. 

 This is united by two or three filaments with the ganglion of the glosso-pharyngeal. 

 It is a true ganglion, containing nerve-cells. After the nerve has emerged from the cra- 

 nial cavity, it presents on its trunk another 

 grayish enlargement, from half an inch to an 

 inch in length, called the ganglion of the trunk. 

 This is of rather a plexiform structure, the 

 white fibres being mixed with grayish fibres 

 and nerve-cells. The exit of the nerve from 

 the cranial cavity is by the jugular foramen, or 

 posterior foramen lacerum, in company with 

 the spinal accessory, the glosso-pharyngeal, and 

 the internal jugular vein. 



Anastomoses, The filaments of communi- 

 cation which the pneumogastric receives from 

 other nerves are interesting from their great 

 importance and their varied sources. The 

 most important of these is the branch from 

 the spinal accessory. There are occasional 

 filaments of communication which pass from 

 the spinal accessory to the ganglion of the root, 

 but these are not constant. After both nerves 

 have emerged from the cranial cavity, an im- 

 portant branch of considerable size passes 

 from the spinal accessory to the pneumogas- 

 tric, with which it becomes closely united. 

 Experiments have shown that these filaments 

 from the spinal accessory pass in great part to 

 the larynx by the inferior laryngeal nerves. 



In the aquseductus Fallopii, the facial nerve 

 gives off a filament of communication to the 

 pneumogastric at the ganglion of the root. 

 This filament, joined at the ganglion by sen- 

 sory filaments from the pneumogastric and 

 some filaments from the glosso-pharyngeal, is 

 called the auricular branch of Arnold. By 

 some anatomists it is regarded as a branch 

 from the facial, and by others it is described with the pneumogastric. 



Two or three small filaments of communication pass from the sublingual to the gan- 

 glion of the trunk of the pneumogastric. 



At the ganglion of the trunk, the pneumogastric generally receives filaments of com- 

 munication from the arcade formed by the anterior branches of the first two cervical 

 nerves. These, however, are not constant. 



The pneumogastric is connected with the sympathetic system by numerous delicate 

 filaments of communication received from the superior cervical ganglion, passing in part 

 upward toward the ganglion of the root of the pneumogastric, and in part transversely 

 and downward. These filaments are frequently short, and they bind, as it were, the 

 sympathetic ganglion to the trunk of the nerve. The main trunk of the pneumogastric 



FIG 218. Anastomoses of the pneumogastric, 

 (Hirschfeld.) 



1, facial nerve : 2, glosso-pharyngeal nerve ; 2', anas- 

 tomoses of the glosso-pharyngeal with the facial ; 

 8, 8, pneumogastric^ with its two ganglia; 4, 4, 

 spinal accessory ; 5. sublingual nerve ; C, superior 

 cervical ganglion of the sympathetic; 7, anasto- 

 mosic arcade of the first two cervical nerves ; 8, 

 carotid branch of the superior cervical ganglion 

 of the sympathetic; 9, nerve of Jacobson; 10, 

 branches of this nerve to the sympathetic; 11, 

 branch to the Eustachian tube ; 12, branch to the 

 fenestra ovaiis; 13, branch to the fenestra rotunda ; 

 14, external deep petrous nerve ; 15, internal deep 

 petrous nerve ; 1(5, otic ganglion ; 17, auricular 

 branch of tlie pneumogastric; IS. anastomosis 

 of tJie pneumogastric with the spinal accessory ; 

 19. anastomosis of the pneumogastric with the 

 sublingual ; 20, anastomosis of the spinal acces- 

 sory with the second pair of cervical nerves ; 21, 

 pharyngeal plexus ; 22, superior Jaryngeal nerve. 



