NERVES OF THE DOGFISH 385 



cephalic and ciliary ganglia were recognized by Beard and by 

 Onodi ('01). The latter examined the structures in the orbit of 

 many selachians and came to the conclusion that the oculomotor 

 ganglion (ciliary) of Schwalbe is a definite isolated ganglion in 

 some spceies, a loose network of cells and fibers in others, and in 

 others still in a form intermediate between these two extremes. 

 In Galeus he finds a loose network; in Mustelus laevistwo ciliary 

 ganglia. These two ganglia are connected with each other by 

 two branches, and each sends a ciliary nerve anteriorly, and a 

 branch posteriorly into the ophthalmic nerve. From the larger 

 of the two ganglia two branches with an oculomotor branch supply 

 the ventral oblique muscle. As recently as 1905 Klinkhardt des- 

 ignated the profundus ganglion in Spinax as ciliary. 



Connected with the oculomotor nerve in Squalus are a number 

 of ganglia, varying in size from a half-dozen cells to many in 

 number. These ganglia are situated on the courses of small 

 non-medullated nerves which as a whole form a plexus." It is 

 not possible in every instance to distinguish the fiber tracts upon 

 which the ganglia are situated, being when in a loose structure 

 so little differentiated from connective tissue. The number and 

 arrangement of the ganglia is subject to individual variation. 

 Moreover, the ganglion cells often occur scattered along their 

 courses instead of being compacted into definite ganglia. There 

 can, however, be distinguished the following general plan of 

 arrangement and number. 



Nothing but densely medullated motor fibers are detected in 

 the intracranial portion of the oculomotor nerve. No intra- 

 cranial ganglion cells, such as Nicholls (T5) finds in Scyllium, 

 are found on the third nerve in Squalus or Mustelus. As the 

 oculomotorius enters the orbit it divides at once into dorsal an- 

 terior and ventral posterior branches. At the point where this 

 forking takes place a small ganglion occurs (figs. 8 and 21, gcil.l). 

 sometimes of only about a half-dozen cells, sometimes within the 

 oculomotor nerve sheath, more often just outside. Regarding 

 the fiber connections of this ganglion there is some uncertainty. 

 Possibly fibers run anteriorly along the anterior division of the 

 oculomotor nerve together with blood-vessels; apparently they 



