490 NERVOUS SYSTEM. 



spinalis. It has the peculiarity, generally, of arising by a sin- 

 gle root, which comes from the anterior chord of the medulla 

 spinalis, between the occiput and the first cervical vertebra. 

 This root consists of from two to six or seven fasciculi, situated 

 one above another. When the posterior root exists, it is very 

 small, is composed of from one to three fasciculi, and anasto- 

 moses with the accessory nerve. 



The trunk of this nerve passes from the vertebral cavity 

 through the foramen formed m the dura mater by the verte- 

 bral artery; it goes out below the latter, and between the oc- 

 ciput and the first vertebra, behind its superior oblique process. 

 It there forms a small long ganglion, like the other spinal 

 nerves, and then divides into an anterior and a posterior fasci- 

 culus. 



The anterior fasciculus is the smaller of the two; it follows, 

 in some measure, the course of the vertebral artery, and going 

 forwards to the front of the transverse process, is then divided 

 into several fine filaments, some of which go to the contiguous 

 muscles on the front of the vertebrae; others join themselves to 

 the pneumogastric and hypoglossal nerves, and to the superior 

 cervical ganglion of the sympathetic; others anastomose with 

 the first cervical nerve. 



The posterior fasciculus runs backwards, and is distributed 

 to the recti and the obliqui muscles on the back of the neck 

 and to the complexus. 



Of the, Cervical Nerves. 



These are seven in number: the first one gets from the 

 spinal cavity between the atlas and the dentata, and the last 

 between the seventh cervical and the first dorsal vertebra. 

 After the ganglion is formed upon the posterior fasciculus of 

 each, the trunk, made by the union of the two fasciculi, di- 

 vides almost immediately again into an anterior and a posterior 

 trunk. 



Of the First Cervical Nerve. 



The posterior trunk is the largest, and goes directly back- 

 wards. It has its filaments distributed to many of the muscles 



