558 



TEXT-BOOK OF PHYSIOLOGY. 



cervical vertebra. 



FIG. 256. SPINAL ACCESSORY NERVE. 

 i. Trunk of the facial nerve. 2, 2. 

 Glosso - pharyngeal nerve. 3, 3. 

 Pneumogastric. 4, 4, 4. Trunk of 

 the spinal accessory. 5. Sublingual 

 nerve. 6. Superior cervical gang- 

 lion. 7, 7. Anastomosis of the first 

 two cervical nerves. 8. Carotid 

 branch of the sympathetic. 9, 10, n, 

 12, 13. Branches of the glosso- 

 pharyngeal. 14, 15. Branches of the 

 facial. 1 6. Otic ganglion. 17. 

 Auricular branch of the pneumogas- 

 tric. 1 8. Anastomosing branch from 

 the spinal accessory to the pneumo- 

 gastric. 19. Anastomosis of the first 

 pair of cervical nerves with the sub- 

 lingual. 20. Anastomosis of the spi- 

 nal accessory with the second pair of 

 cervical nerves. 21. Pharyngeal 

 plexus. 22. Superior laryngeal 

 nerve. 23. External laryngeal 

 nerve. 24. Middle cervical gang- 

 lion. (H irschfeld.) 



rise to muscle contraction. 



From this origin the fibers pass to the surface of 

 the cord to emerge between the 

 ventral and dorsal roots in from 

 six to eight filaments, after which 

 they unite from below upward 

 to form a distinct nerve. This 

 enters the cranial cavity through 

 the foramen magnum, where it 

 joins with the medullary portion 

 to form the common trunk, 

 which then passes forward to 

 emerge from the cranium 

 through the jugular foramen. 



Distribution. After emerg- 

 ing from the cranial cavity the 

 nerve soon separates into two 

 branches : 



1. An internal or anastomotic 



branch, consisting chiefly 

 of filaments coming from 

 the medulla oblongata. It 

 soon enters the trunk of 

 the vagus, from which 

 fibers pass to the muscles of 

 the pharynx, to the muscles 

 of the larynx through the 

 inferior laryngeal nerve, 

 and to the heart accord- 

 ing to most authorities. 



2. An external branch, consist- 



ing chiefly of the accessory 

 fibers from the spinal cord. 

 It is distributed to the 

 sterno-cleido-mastoid and 

 trapezius muscles. 

 Cortical Connections. The 

 nucleus of origin of the medul- 

 lary branch at least is in relation 

 with nerve-cells in the lower 

 third of the general cerebral 

 motor area, the axons of which 

 descend in the pyramidal tract. 

 Properties. Faradization of 

 the nerve near its origin gives 

 Destruction of the medullary root is 



