THE ENCEPHALIC OR CRANIAL NERVES 



639 



reflex actions which are highly essential to the life of the individual, e.g., 

 respiration, the heart-beat, blood-pressure, etc., all of which have been con- 

 sidered in foregoing pages. 



THE ELEVENTH NERVE. THE SPINAL ACCESSORY 



The eleventh cranial nerve, the spinal accessory, consists of peripherally 



coursing fibers which bring the nerve-cells 



from which they arise into relation with 



separate but functionally related muscles, 



such as those entering into the formation 



of the larynx. It consists of two por- 

 tions, the medullary or bulbar and the 



spinal. 



Origin. The axons comprising the 



medullary portion arise from a group of 



nerve-cells in the extreme lower part of 



the nucleus ambiguus, known as the nidus 



laryngei. From this origin the axons 



pass forward and outward to emerge from 



the medulla just below and in series with 



the roots of the vagus nerve. 



The axons comprising the spinal por- 

 tion have their origin in nerve-cells in 



the lateral margin of the anterior horn 



of the gray matter in the cervical portion 



of the cord as far down as the fifth cer- 

 vical vertebra. 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 mag- 

 num, 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. 



(Fig. 272.) 



Distribution. After emerging from 



the cranial cavity the nerve soon sepa^ 



rates into two branches: 



i. An internal or anastomotic branch, 

 consisting chiefly of filaments com- 

 ing from the medulla oblongata. It 

 soons enters the trunk of the vagus, 

 from which fibers pass through the 

 pharyngeal plexus to the superior 



and inferior constrictor muscles of the pharynx, to thepalato-pharyngeus, 

 to the levator palati and azygos uvulae muscles (Beevor and Horsley) ; to 



Glosso-pharyngeal nerve. 3, 3. Pneumo- 



gastric. 4,4,4- Trunk of the spinal acces- 



sory. S. Sublingual nerve. 6. Superior 



cer vi ca i ganglion. 7, 7. Anastomosis of 



the first two cervical nerves. 8. Carotid 



14, 15. Branches of the facial. 16. Otic 

 ganglion. 17. Auricular branch of the 

 pneumogastric. 18. Anastomosing branch 

 from the spinal accessory to the pneu- 

 mogastric. 19. Anastomosis of the first 



with the Sec0 nd pair of cervical nerves. 21. 

 Pharyngeal plexus. 22. Superior laryn- 



