CoGHiLL, Crajiial Neit'cs of Ainblyst07na. 213 



the innervation of the m. rectus inferior. The ciliary ganglion 

 is transitory, and probably at no time functional. 



It will be noticed, also, in these cases, that the inferior 

 branch of the third nerve may pass either dorsally or ventrally 

 of the m. rectus internus to reach the m. rectus inferior, that 

 it may approach either the dorsal or ventral surface of the m. 

 rectus inferior. Again, it may penetrate the latter muscle on 

 its way to the m. obliquus inferior. It may or may not bear a 

 ciliary ganglion. 



2. — The Trochlear Nerve. 



The fourth nerve emerges from the dorsal surface of the 

 brain, near the middle line in the angle between the optic lobes 

 and the cerebellum. It passes dorso-cephalad to its foramen in 

 the parietal bone. Outside the foramen it passes cephalad 

 closely compressed between the cranium and the temporalis 

 muscle. On emerging from this position at the anterior margin 

 of the muscle, it inclines ventrad and meets a branch of the 

 ophthalmicus profundus. I find no positive evidence of an 

 anastomosis in this case, although the nerves are in very inti- 

 mate relation with each other. The fourth nerve is penetrated 

 by the trigeminal twig, and then passes through the m. levator 

 bulbi and innervates the m. obliquus superior. 



^. — The Abdiicens. 



The sixth nerve emerges from the ventral side of the 

 medulla some distance posteriorly of the roots of the seventh 

 nerve. It passes cephalad ventrally of these roots. It is 

 usually removed some distance from the roots of the fifth, but 

 in younger specimens it may be closely compressed against the 

 ventral surface of these nerves. Its course lies ventrally of the 

 trigeminal roots until it reaches the Ga$serian ganglion. The 

 abducens then becomes closely applied to the ventral surface of 

 that part of the ganglion which belongs to the ophthalmicus 

 profundus. It always becomes^enveloped by the ganglion cells 

 for- a short distance. I find no direct evidence to show that 

 trigeminal fibers enter the sixth nerve within the Gasserian 



