NERVES OF THE DOGFISH 331 



of the sympathetic system. The medullated fibers are dis- 

 tributed to the wall of the eyeball, passing into the interior by 

 small foramina through the sclerotic cartilage. Although di- 

 verse in character and distribution, these fibers given off from 

 the posterior region of the ramus ophthalmicus profundus may 

 be termed the posterior ciliary nerve. The medullated ones 

 seem to represent the ciliares longi in part. 



At the level where the trochlear nerve is passing ventrally 

 around the ramus ophthalmicus superficialis VII the ramus 

 ophthalmicus profundus running a little ventral to the other 

 nerves gives off a small branch distributed to the external mem- 

 branous portion of the sclerotic coat, a small twig passing intern- 

 ally through the cartilaginous portion (figs. 35 and 51, cila.). 

 This anterior branch may be termed the anterior ciliary nerve. 

 Between the anterior and posterior ciliary nerves a very minute 

 twig is sent from the r. oph. prof, into the sclerotic coat. The 

 branches of the profundus distributed to the eyeball appear to 

 be the equivalent of the long ciliary nerves of higher forms. 



Slightly anterior to the origin of the anterior ciliary nerve 

 another branch leaves the ramus oph. prof. It runs anteriorly 

 across the dorsal oblique muscle on the ventrolateral face of the 

 latter, then at the anterodorsal border of the same muscle turns 

 mesially and dorsally, and at the anteromesial border of the 

 foramen by which the r. oph. spf. VII passes to the dorsal bor- 

 der of the skull, runs by its own small foramen to the dorsal 

 side of the cranium. Passing anteriorly, it is distributed to the 

 skin lateral to the supraorbital canal. 



The ramus ophthalmicus profundus in Mustelus on entering 

 the orbit gives off a posterior ciliary nerve, also a ciliary branch 

 that unites with the ventral division of the oculomotorius. It 

 then passes through the Y-shaped fork of the rectus internus 

 muscle, meeting the oculomotorius passing in the reverse direc- 

 tion. Anteriorly the profundus passes at the ventral border of 

 the rectus internus, becoming closely applied to the mesial wall 

 of the eyeball. It gives off an anterior ciliary nerve that enters 

 the eyeball on its anterior border. At the level of the origin of 

 the dorsal oblique muscle it passes through the posterior part of 



