392 NERVES OF THE BRAIN. 



pass forwards and downwards, and penetrate the dura mater 

 near the point of the petrous portion of the temporal bone. 



This nerve appears like a bundle of fibres; and, under the 

 dura mater, forms a plexus ; from which its three great branches 

 proceed to their destination. 



The sixth pair arise from the medulla oblongata, where it 

 joins the pons varolii. It is often composed of two chords on 

 each side, one of which is^ery small; they pass under the 

 pons Varolii, and through the cavernous sinus, with the carotid 

 artery : after emerging from this sinus they proceed through 

 the foramen lacerum to the abductor muscles of the eye. In 

 this course a small twig passes from it, which accompanies the 

 carotid artery through the canal in the petrous portion of the 

 temporal bone, and with a twig from the fifth pair, is the origin 

 of the intercostal nerve. 



The seventh pair appear at the side of the medulla oblongata, 

 near the pons Varolii. It is composed on each side of two 

 chords, called Portia Dura and Portio Mollis, and of one or 

 more small fibres between them, called Portio Media. The 

 portio mollis can be traced to the fourth ventricle. The portio 

 dura seems to arise from the place of union of the pons Varolii 

 with the medulla oblongata and the crura cerebelli. The portio 

 media appears to originate in the same neighborhood, and 

 may be considered as an appurtenance of the portio dura. 

 They all proceed to the meatus auditorius internus, as it has 

 been called, in the temporal bone. 



The eighth pair of nerves arise from the corpora olivaria on 

 the side of the medulla oblongata. They are composed in each, 

 of one chord called the Glosso-Pharyngeal, and of a conside- 

 rable number of small filaments, which unite and form another 

 chord called the Par Vagum. 



With these nerves is associated a third chord, called the 

 Spinal Accessory Nerve of Willis, which passes up the spinal 

 cavity, being composed of twigs from the posterior and ante- 

 rior portions of almost all the cervical nerves. 



The par vagum, with this nerve and the glosso-pharyngeal, 

 proceeds from its origin to the foramen lacerum formed by the 



