THE CRANIAL NERVES. 75 



Then trace the muscle back below the optic nerve to 

 its origin from the base of the skull beneath the ante- 

 rior clinoid processes. 



189. Pushing the eyeball aside, trace forward below 

 it the branch of the third nerve which enters the in- 

 ferior oblique muscle near its origin. Then remove 

 the eyeball and its muscles entirely. 



190. Seek in the loose tissue covering the floor of 

 the orbit for the superior maxillary nerve, a branch of 

 the fifth cranial. Having found it, cut away the bony 

 arch covering in the temporal fossa, and trace the nerve 

 back through the mass of muscles occupying that re- 

 gion of the skull, until it reaches its foramen of exit 

 (27, b) ; then, carefully cutting the bone away as re- 

 quired, trace the trunk to the Gasserian ganglion. Im- 

 mediately after passing out of the skull, the nerve gives 

 ofE a branch which enters the muscles lying around it. 

 It then runs forward to the orbit, which it enters at its 

 inner side and close to its floor, and there divides into 

 two branches. The smaller of these passes forward 

 and outward, and disappears through a foramen in 

 the anterior region of the floor of the orbit. The lar- 

 ger branch runs forward in a more internal course and 

 passes through the membranous region (29) of the or- 

 bital floor to enter the nasal cavity. 



191. The inferior maxillary nerve leaves the skull by 

 the same foramen as the superior, and may there be 

 readily found on the ventral side of the latter and 

 traced back to the ganglion. After getting outside the 

 skull it gives off several small branches to the neigh- 



