GLOSSO-PHARYNGEAL NERVE. Ill 



On the pneumogastric trunk the student should define an enlargement 

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

 is intimately united. From the ganglion proceed two branches (pharyn- 

 geal and laryngeal), which are to be traced to the parts indicated by their 

 names, especially the first which enters the pharyngeal plexus. The task 

 of disentangling the ramifications of the branch of the 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 recognized readily. Lastly the dissector may 

 prepare more fully the recurrent branch coursing up beneath the lower 

 part of the common carotid : by removing the fat around it, offsets will be 

 seen entering 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 nerves are to be demonstrated. 



A dissection for the sympathetic will be given further on (p. 116); but 

 its large ganglion near the skull (upper cervical) should be defined, and 

 the small branches from it to the pharyngeal plexus should be pursued 

 beneath the carotid artery. 



The three cranial nerves, glosso-pharyngeal, pneumogastric, and spinal 

 accessory, which constitute the eighth nerve of Willis, leave the cranium 

 by the foramen jugulare (p. 32). Outside the skull the nerves take dif- 

 ferent directions according to their destination ; thus the glosso-pharyngeal 

 is inclined inwards to the tongue and pharynx ; the spinal accessory back- 

 wards to the sterno-mastoid and trapezius muscles ; and the pneumogastric 

 nerve descends to the viscera of the thorax and abdomen. 



The GLOSSO-PHARYNGEAL NERVE (fig. 26, ') is the smallest of the three 

 trunks. In the jugular foramen it is placed somewhat in front of the other 

 two, and lies in a groove in the lower border of the petrous part of the tem- 

 poral bone. In the aperture of exit the nerve is marked by two ganglionic 

 swellings, the upper one being the jugular, and the lower the petrous ganglion. 



* Ganglia. The jugular ganglion, 4 , (ganglion superius) is very small, 

 and is situate at the upper part of the osseous groove containing the nerve. 

 It is placed on the outer surface of the glosso-pharyngeal trunk, and in- 

 cludes only some fibrils of the nerve. The petrosal ganglion, 5 , (gang, 

 inferius) is mucli larger than the preceding, and incloses all the fibrils of 

 the nerve. Ovalish in form, it is placed in a hollow in the lower border 

 of the temporal bone ; and from it spring the branches that unite the glosso- 

 pharyngeal with other nerves. 



After the nerve has quitted the foramen it comes forwards between the 

 jugular vein and the carotid artery (fig. 25, '), and crossing inwards over 

 the artery, reaches the lower border of the stylo-pharyngeus muscle. At 

 this spot the nerve becomes almost transverse in direction in its course to 

 the pharynx ; it crosses over the stylo-pharyngeus, and forms an arch 

 across the side of the neck above the superior laryngeal nerve. Finally 

 it passes beneath the hyo-glossus muscle, and ends in branches to the 

 pharynx, the tonsil, and the tongue. 



The branches of the glosso-pharyngeal may be classed into those con- 

 necting it with other nerves at the base of the skull, and those distributed 

 in the neck. 



* Connecting branches arise chiefly from the petrosal ganglion ; and in 

 this set is the tympanic nerve. 



