PNEUMOGASTEIC KEKVE. 205 



median line, but more recent observations leave no doubt 

 of the fact that many of these fibres decussate in the floor 

 of the fourth ventricle. 1 



There are two ganglionic enlargements belonging to the 

 pneumogastric. In the jugular foramen, is a well-marked, 

 grayish, ovoid enlargement, from one-sixth to one-fourth of 

 an inch in length, called the jugular ganglion, or the gan- 

 glion of the root. This is united by two or three filaments 

 with the ganglion of the glosso-pharyngeal. It is a true gan- 

 glion, containing nerve-cells. After the nerve has emerged 

 from the cranial 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 communication 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 acces- 

 sory. There are occasional filaments of communication 

 which pass from the spinal accessory to the ganglion of the 

 root, but they are not constant. After both nerves have 

 emerged from the cranial cavity, an important branch of 

 considerable size passes from the spinal accessory to the 

 pneumogastric, with which it becomes closely united. Ex- 

 periments 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 



1 DEAN, The Gray Substance of the Medulla Oblongata and Trapezium, Wash- 

 ington, 1864, p. 27. 



