CRANIAL NERVES. 279 



Turn the eye up ; trace the nerve across the 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 median 

 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 

 ophthalmic branch of the fifth nerve. It 

 supplies the sensory ampullae and sensory 

 canal of the supra-orbital region. 



