424 NERVES OF ENCEPHALON. 



nerve, and, according to Mr. Bell, lias its origin from the 

 respiratory tract. It enters the foramen auditorium inter- 

 num, passes along the aqueduct of Fallopius, and emerges 

 at the stylo-mastoid foramen, from whence it is distributed 

 to the muscles of expression. 



The portio mollis, or auditory nerve, is the larger of the 

 two, and the most posterior. It arises from the side of the 

 calamus scriptorius, the floor of the fourth ventricle, and the 

 corpus restiforme,})y several filaments which form a very soft, 

 white cord ; then unites with the portio dura, and enters 

 along with it, the internal auditory foramen, from which, 

 at the hase of this canal, it separates and goes to supply 

 the internal ear, as the cochlea, semicircular canals, &c. 

 This nerve is the nerve of hearing. 



The Eighth Pair consists of the Glosso Pliaryngeal, (Figs. 

 91, 118,) Pneumogastric, or par vagum, and the Spinal 

 accessory. 



The glosso pharyngeal arises, by four or six filaments, 

 from the fissure between the olivary and restiform bodies, 

 or from the respiratory tract; these unite into a small 

 nerve which joins the par vagum. The par vagum, or pneu- 

 mogastric, arises below the last, in the same groove between 

 the corpus olivare and corpus restiforme, by ten or fifteen 

 filaments, which, uniting together, form a larger nerve 

 than the glosso-pharyngeal ; the two now proceed together 

 to the foramen lacerum posterius, where they are joined by 

 the third portion the spinal accessory. This latter nerve 

 arises low in the neck as low as the fourth or fifth verte- 

 bra, and occasionally as low as the seventh cervical, by 

 several filaments from the respiratory tract on the sides 

 of the medulla spinalis, between the roots of the anterior 

 and posterior spinal nerves ; it ascends behind the liga- 

 mentum denticulatum, receiving filaments from the spinal 

 nerves, in its ascent, and after entering the foramen inag- 

 nus, proceeds to the foramen lacerum posterius, where it 

 joins the other portions of the eighth pair. They all 

 pass through the foramen lacerum posterius, anterior to 

 the jugular vein, and then each proceeds to its peculiar 



