246 THE DOG-FISH 



The part of the sixth nerve within the skull can only be. 

 seen after the brain is removed. In the orbit the nerve can 

 be seen along the inferior border of the rectus externus. 



The seventh or facial nerve, like 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 ophthalmic 

 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 tlae-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. 



v ii. The palatine nerve is a slender nerve which runs 

 forwards and outwards across the floor of the 

 orbit, immediately behind the main stem of 

 the fifth nerve : it then turns forwards be- 

 neath this nerve and runs along the upper jaw, 

 sending branches to the roof of the mouth. 

 ^ iii. The hyoidean or post-spiracular nerve is a 

 much stouter nerve, which runs straight out- 

 wards along the posterior wall of the orbit 

 towards the spiracle. Continuing its course 

 outwards and backwards, in close contact with 

 the anterior wall of the auditory capsule, it 

 passes along the posterior border of the 



