330 H. W. NORMS AND SALLY P. HUGHES 



3. The ramus ophthalmicus profundus V 



The profundus nerve leaves its ganglion slightly posterior to 

 the distal tip of the latter, on its dorsolateral border (fig. 10). 

 Leaving the ganglion, it swings out dorsolaterally in a 'gradual 

 curve through the orbit anteriorly, passing ventral to the dorsal 

 rectus muscle (figs. 5 to 7), grazing the mesial wall of the eye- 

 ball, again approaching the ramus ophthalmicus superficialis 

 VII so as to pass along the ventral border of the latter close 

 to the skull (fig. 15). Anterior to the emergence of the 

 trochlearis nerve the profundus separates from the facial super- 

 ficial ophthalmic, passes ventral to the dorsal oblique muscle 

 (fig. 15), then rising dorsally, at the level of the anterior wall 

 of the eyeball passing through a long narrow canal in the cranial 

 wall, it emerges on the dorsal side of the skull, just dorsal to the 

 olfactory bulb (figs. 35 and 51). .It divides within the canal 

 into two portions, and on emerging is distributed to the skin of 

 the snout dorsally and laterally. In its course from the ganglion 

 to its final distribution the ophthalmicus profundus gives off 

 three branches, the posterior two of which are the anterior and 

 posterior ciliary nerves (figs. 21, 22, 35, and 51, cila., dip.). 



As the ramus ophthalmicus profundus leaves its ganglion 

 there may be recognized at its lateral border a small but dis- 

 tinct bundle of fibers, which may be traced back within the 

 ganglion (figs. 6 to 11, cilp.). At no place does this small bundle 

 appear to be closely associated with the other fibers of the nerve. 

 Near the level of the exit of the oculomotor nerve, as the pro- 

 fundus nerve is passing ventral to the dorsal rectus muscle and 

 near the posteromesial border of the eyeball, this small strand 

 of fibers separates spatially from the main nerve (fig. 6, clip.). 

 The fibers of this small strand are all well medullated. At the 

 point of emergence from the profundus, however, non-medul- 

 lated fibers appear as a distinct tract. In some specimens these 

 fibers can be traced back into the ganglion. On leaving the 

 profundus nerve flic non-medullated fibers pass ventrally and 

 posteriorly to join the ciliary plexus (figs. 6 to 8, cilrl.). Their 

 subsequent course will be described in the account given later 



