50 
Proceedings of Royal Society of Edinburgh. [sess. 
nerve, which, being joined by a similar nerve from the profundus 
division of the Vth, swells to form the ciliary ganglion, and this, 
on being teased, was seen to contain large nerve cells. From the 
ciliary ganglion two ciliary nerves with the characteristic wavy 
course proceed to the eye. This account of the ciliary ganglion 
agrees with that described in Lcemargus by Ewart, but I should 
like to leave the matter in Cliimcera an open one, as I only dis- 
sected the ciliary ganglion on one side, and then, owing to the 
parts having been disturbed by previous dissection, not as carefully 
as I could have wished. 
Fourth Nerve. — Arises, as in all vertebrates, from the roof of 
the Sylvian aqueduct, and emerges from the brain in the perpen- 
dicular furrow between the optic lobes and cerebellum. It courses 
upwards and forwards, and reaches the orbit under cover of the 
superficial ophthalmic division of the Vllth. It is obscured by the 
latter for the greater part of its course, but finally takes a dorsal 
curve and supplies the superior oblique muscle of the eye. 
Fifth Nerve . — This nerve is in a more primitive condition than in 
any vertebrate yet described, and its distribution, therefore, is some- 
what important. It arises from the medulla by two closely applied 
roots under cover of the buccal root of the Vllth. These two 
roots fuse indissolubly, and neither they nor their product mingle 
with the roots of the Vllth, or in any way become inseparable 
from them. The Vth nerve, therefore, may be followed through- 
out almost the whole of its course without the confusing elements 
which mixed roots inevitably introduce.* The Vth, after passing 
through the same foramen which gives exit to the buccal and 
hyomandibular divisions of the Vllth, immediately expands into 
the large Gasserian ganglion, and I distinguish five branches as 
follows : — 
(a.) Superficial ophthalmic. ) 
; l Dorsal branches. 
( b .) Profundus. j 
(c.) Maxillary (prse-branchial). 
(d.) Mandibular (post-branchial). 
(e.) Pharyngeal or Visceral. 
* There may be an exchange of very fine fibres between the roots of Vth 
and Vllth, and the outer buccal division of the Vllth I have seen connected 
with the maxillary division of the Vth, but these are obviously questions of 
detail. 
