CRANIAL NERVES. 271 



Ttirn the eye tip ; trace the nerve across tJie floor of the 

 orbit, and follow its branches to their distribution. 



ii. The maxillary branch, -which is the anterior of 

 the three, turns over the upper jaw at the 

 anterior border of the orbit, and divides into 

 branches which run forwards to supply the 

 region of the upper jaw. 



iii. The mandibular branch, the posterior of the 

 three, crosses the upper jaw, and then curving 

 round the angle .of the mouth, where it lies 

 very close to the surface, runs forwards along 

 the lower jaw. It supplies the muscles moving 

 the lower jaw. 



6. The sixth nerve is very slender, and arises from the 



ventral surface of the medulla near the inedian plane, 

 and a short way behind the roots of the fifth and 

 seventh nerves ; it passes out through the same 

 foramen with these nerves, lying below them and 

 separated from them by dense connective tissue. It 

 supplies the rectus externus. 



To see the part of the sixth nerve within the skull, cut 

 through the roots of the fifth and seventh nerves, and press 

 the brain aside. In the orbit the nerve can be seen along the 

 inferior border of the rectus externus. 



7. The seventh or facial nerve has four main branches. 



i. The ophthalmic branch arises from the dorsal 

 edge of the medulla, immediately behind the 

 cerebellum. It runs forwards for about a 

 quarter of an inch within the skull, and then 

 enters the orbit through a foramen above and 

 a little behind the origins of the recti muscles. 

 In the orbit it runs forwards close to the skull- 

 wall, alongside of and dorsal to the ophthal- 

 mic branch of the fifth nerve. It supplies 

 the sensory ampuUte and sensory canal of the 

 supra-orbital region, 



