THE CRANIAL NERVES. 6/ 



b. Behind this the main portion of the right or- 

 bital fossa, containing the eyeball and ntiost of 

 its muscles, and the outer part of the optic 

 nerve attached to the globe. Entering the 

 orbit behind and running forward near its roof 

 will be seen a slender branch of the third 

 nerve. 



174. Behind the orbit is a thin plate of the parietal 

 bone (45), separating the cranial cavity from the tempo- 

 ral fossa. On its inner side will be found the sixth 

 nerve, running forward to the orbit, through which 

 cavity it may be traced to the external rectus muscle. 

 On the inner surface of the bone is also a, fossa, or de- 

 pression, opposite the back part of the cerebral hemi- 

 sphere and the front of the mid-brain, and placed be- 

 tween the parietal and prootic bones. Pull away the 

 dura mater which covers this pit, and the large Gasserian 

 ganglion will be exposed, with the sensory root of the 

 fifth cranial nerve entering it. Proceeding forward 

 from the ganglion, will be found the stump of the orbito- 

 nasal nerve, the peripheral part of which has already 

 been seen (168, d). 



175. Posterior to the fifth nerve, the seventh of the 

 right side will be seen, entering a foramen in the cranial 

 wall ; and, close behind it, the smaller eighth {auditory) 

 nerve, entering the auditory capsule. Above its point 

 of entry the inner wall of the labyrinth is cartilaginous. 



176. Still farther back is the foramen of exit for the 

 tenth and eleventh nerves {pneumogastric and spinal ac- 

 cessory). 



