EXPOSURE OF THE CRANIAL NERVES. 631 



Below tlw foramen of exit from the skull, the cranial nerves have Dissection 

 been for the most part denuded by the dissection of the internal nerves in 

 carotid: but the intercommunications of the vagus, hypoglossal, the neck : 

 sympathetic, and first two spinal nerves, near the skull, are to be 

 traced out more completely. 



The larger part of the spinal accessory has been sufficiently laid of spinal 

 bare already ; but its small part is to be traced to the vagus close ac 

 to the skull, and onwards along that trunk. 



The chief part of the glosso-pharyngeal has also been dissected ; of glosso- 

 but the offsets on the carotid, and others to the pharynx in front of P^ryngeal ; 

 the artery are to be defined. 



On the pneumo-gastric trunk the student will find an enlargement of vagus ; 

 close to the skull (ganglion of the trunk), to which the hypoglossal 

 nerve is intimately united. From the ganglion proceed two branches 

 (pharyngeal and laryngeal), which are to be traced to the parts indi- 

 cated by their names, especially the first which enters the pharyngeal pharyngeal 

 plexus. The task of exposing the ramifications of the branch of the P 

 vagus, and those of the glosso-pharyngeal and sympathetic in the 

 plexus, is by no means easy, in consequence of the dense tissue in 

 which they are contained. Two or more cardiac offsets of the vagus, 

 one at the upper and another at the lower part of the neck, may be 

 recognised readily. Lastly, the dissector may prepare more fully and re 

 the recurrent branch coursing up beneath the lower end of the 

 common carotid ; by removing the fat around it, offsets may be seen 

 passing to the chest and the windpipe. 



Only the first, or the deep part of the hypoglossal nerve remains 

 to be made ready for learning ; its communications with the vagus, 

 sympathetic, and the spinal nerve are to be shown. 



A dissection for the sympathetic will be given farther on (p. 636) ; 

 but its large ganglion near the skull (upper cervical) should be part, 

 cleaned, and the branches from it to the pharyngeal plexus should be 

 pursued beneath the carotid artery. 



The ninth, truth, and eleventh cranial nerves (glosso-pharvngeal, Ninth, tenth 

 . , . , . "i i and eleventh 



pneumo-gastric, and spinal accessory) leave the cranium together by nerves. 



the jugular foramen, from which circumstance they were formerly 

 grouped together as one nerve the eighth nerve of Willis. Outside 

 the skull the nerves take different directions to their destination ; 

 thus the glosso-pharyngeal is inclined forwards to the tongue and 

 pharynx over the internal carotid artery ; the spinal accessory back- 

 wards to the sterno-mastoid and trapezius muscles over the internal 

 jugular vein ; and the pneumo-gastric nerve descends to the viscera 

 of the thorax and abdomen lying in the carotid sheath for a 

 considerable distance. 



The GLOSSO-PHAEYNGEAL NERVE (figs. 225, i and 226, l ) is the Gloss - 



uliarvii^ 



smallest of the three trunks. In the jugular foramen it is placed some- nerve 

 what in front of the other two, and lies in a groove in the hinder 

 border of the petrous part of the temporal bone. In the aperture of ha ^ tjjo. 

 exit the nerve is marked by two ganglionic swellings, the upper one foramen, 

 being the jugular, and the lower the petrosal ganglion. 



