THE NERVOUS SYSTEM 135 



Eye-muscle Nerves (PI. XIII, fig. 57). 



In addition to the general accounts already referred to, Schwalbe 

 in 1879 published a description of the eye-muscle and ciliary nerves. 

 He, like Fischer, fails to find the oculomotor branch to the M. rectus 

 superior, but he disagrees with him in that he does sometimes find 

 a N. trochlearis to be present. He is the first to give an account of 

 the ciliary nerves, both superior and inferior, although he is a little 

 uncertain of the exact relations of the latter. 



Owing partly to the small size of the animal, and partly to the 

 rather large amount of individual variation met with, the investiga- 

 tion of these nerves in the Salamander is by no means easy, but with 

 care they may be followed fairly satisfactorily with the aid of a bino- 

 cular dissecting microscope. 



III. N. Oculomotorius (n.3) (somatic motor). The IlIrd nerve 

 leaves the brain from the floor of the mesencephalon and passes out 

 of the cranial cavity through a special foramen — For. oculomotorium 

 — in the side wall of the cranium, just posterior to the optic fenestra. 

 Within the orbit it divides into two rami. 



(a) A ramus superior which turns dorsalwards and enters the M. 

 rectus superior along its anterior border. 



(F) A ramus inferior which passes ventralwards, posterior to the 

 optic nerve, between it and the M. retractor bulbi, and close to a 

 branch of the Vth nerve. It divides into three branches, going respec- 

 tively to the inferior and anterior rectus muscles, and to the inferior 

 oblique muscle. Throughout its course it keeps close to the trige- 

 minal branch above mentioned, and apparently passes across, or 

 through it, above the M. rectus inferior. 



(c) Close to the point where the N. oculomotorius divides into 

 superior and inferior rami a ramus communicans to the R. ophthalmicus 

 profundus V may be found (n.3-5), and usually at about the same 

 point a slight swelling of the nerve represents the ciliary ganglion. 

 Schwalbe (i 879) reports several patches of ganglionic cells along the 

 course of the ramus inferior, of which the largest is in the position 

 indicated above. Hoffmann (1902) also confirms the presence of 

 ganglia associated with the oculomotor nerve, but says that they sur- 

 round the nerve like a sheath and are not within the nerve itself, while 

 he considers them to be of a sympathetic nature and to represent the 

 most anterior ganglion of this system. Coghill finds in Amblystoma 

 that the ciliary ganglion is transitory, and tends to disappear in the 

 adult. Hence he concludes that it is at no time functional. 



It is certain, however, that a ganglion does normally occur associated 



