THE CRANIAL NERVES OP SCYLLIUM. 89 



it differs from the condition described above chiefly in not possessing 

 anterior non-ganglionic roots, and in not having its terminal branches 

 fully developed. At stages later than n the nerve seems to arise from 

 the base of the mid brain by a single large ganglionic root, no smaller 

 non-ganglionic ones being visible (fig. 14, in), though at stage n itself 

 they are very prominent (fig. 13, hi). 



Besides the branches of the third nerve, mentioned above, there are 

 two others in direct connection with the ganglion e.g. : of these the 

 first, at stage l (fig. 10, JV.c), is a short nerve, which lies along the 

 top of the second head cavity and serves to connect directly the 

 ganglion e.g. of the third nerve with the Gasserian ganglion at the 

 root of the fifth. 



The second (figs. 10, 11, and 12, iV) passes straight forward from the 

 ganglion e.g. running through the walls of the first head cavity under 

 the rectus superior and rectus internus, and through the substance of 

 the sclerotic on the inner surface of the eyeball. Passing out from the 

 orbit, immediately above the obliqiius inferior, it still pursues its 

 course straight forward, but becomes more superficial. In the earlier 

 stages it crosses the root of the olfactory nerve, with which it lies in 

 very close contact : in the later stages (figs. 12 and 15, n) it is rather 

 more dorsally situated, and crosses the ophthalmic branches of the 

 fifth and seventh nerves at a considerable angle (fig. 12, n), ending 

 in the skin at the extreme fore part of the head. After careful and 

 repeated examination we have failed to detect any branch given off 

 from the nerve at any point of its length. 



At stage K all the above-mentioned branches of the third nerve are 

 developed, except the upper branch, to the rectus superior and rectus 

 internus, which we have failed to detect : the ganglion e.g. is very 

 conspicuous, and the nerves JV.c. and iT. have the same structure and 

 connections as at stage N, the latter of the two stretching forward to 

 the extreme anterior part of the head, in the skin at which it ends. 



In the later stages the modifications which the third nerve 

 undergoes are merely ones of detail, all the principal branches of the 

 nerve being already established, and maintaining their relations prac- 

 tically unaltered in the adult. The most important changes concern 

 the gangliou e.g.; this, which at stages k and l is a large prominent 

 swelling (fig. 10, e.g.), in the later stages becomes far less conspicuous, 

 and the ganglion cells, instead of being concentrated at one spot, 

 occur in small scattered patches at different parts of the nerve* This 



