NERVOUS SYSTEM. 341 



transmitting other smaller filaments to the superjacent skin. 

 Against the articulation of tiie posterior jaw, the portio dura is 

 joined by a considerable branch from the posterior maxillary 

 nerve. Augmented in size by this contribution, the portio dura 

 emerges from the substance of the gland and turns round the 

 cervix of the jaw, along the outward side of the temporal artery. 

 Having mounted upon the masseter, it divides into two princi- 

 pal branches. The posterior one obliquely crosses the muscle a 

 little anteriorly to its middle, enveloped in cellular membrane, 

 detaching many filaments in its passage to the fibres of the mus- 

 cle, but more and larger ones to the skin, and some few of com- 

 munication with the anterior branch, and ultimately ramifies 

 subcutaneously upon the muscles of the lower lip, and side of 

 the lower jaw. The anterior branch descends over the fore part 

 of the masseter, a little posteriorly to the zygoma, likewise 

 clothed in cellular substance, furnishing, in its course, muscular, 

 cutaneous, and communicating filaments. Leaving the masseter, 

 it inclines forward, undiminished in size, from the ramifications 

 it has already issued, and, shortly after, ends in an arborescent 

 expansion, which spreads its fibrils over the inferior and anterior 

 parts of the face. It sends some twigs to the muscles there- 

 abouts, and to the upper lip ; but the principal ramifications run 

 to join those of the anterior maxillary nerve. 



Eighth Pair, or Par Vagum. 



This pair is constituted of two nerves on either side, so that 

 it may be said to be double: — the accessory, or additional one, 

 is denominated the glosso-pharyngeus ; the other is the proper 

 par vagum. They arise by many filaments from the corpora oli- 

 varia, and make their exit through the foramina lacera basis 

 craiiii, in company with the nerves next to be described. Having 

 left the skull, we find them lodged, secure from injury, along 

 with the nerve of the ninth pair, in a hollow space to the inward 

 side of the condyloid process of the occiput, 



THE GLOSSO-PHARYNGEUS, by much the smaller of 

 the two, now quits the par vagum, and, turning round the in- 

 ternal carotid artery, runs forward and downward upon the side 

 of the pharynx, insinuating; itself among the constrictors, whence 

 it proceeds to the root of the tongue, and there disappears. Its 

 branches are— 1. At its origin, a reflected branch, which joins 

 the portio dura just before that nerve pierces the parotid gland. 

 2. Two branches to the constrictors of the pharynx. 3. Before 

 it reaches the tongue, the nerve splits into three or four branches, 

 which ramify and vanish in the base or root of that organ. 



