CRANIAL NERVES 25S 



iii. The mandibular branch, the posterior and 

 smaller of the two, 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 extemus. 



The part of the sixth nerve within the skull may be seen 



by cutting through the roots of the fifth and seventh nerves, 



and pressing the brain aside. In the orbit the nerve can be 



seen along the inferior border of the rectus extemus. 



7. The seventh or facial nerve, hke the fifth, has three 



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, which it accom- 

 panies to its distribution. 

 The root is large and readily seen on pressing the brain 

 away from the skull. The dissection is the same as for the 

 corresponding branch of the fifth nerve. 



The main stem of the seventh nerve enters the 

 orbit immediately behind the fifth, and divides almost 

 at once into two main branches. 

 Turn the eye up and dissect from the side, following the 

 branches to their distribution. 



