42 Dixon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
Since the ramus ophthalmicus profundus of Elasmobranchs represents the nasal 
of mammals, it is interesting to quire whether there is any nerve in Elasmo- 
branchs to represent the frontal of mammals. Marshall and Spencer describe the 
ophthalmic branch of the fifth nerve in Scyllium as lying ‘“ dorsal to all the eye 
muscles and other contents of the orbit.” This ophthalmic branch of the fifth in 
Scyllium rises from the Gasserian ganglion directly ; and, though in the embryo 
at first perfectly distinct, it is in the adult more or less closely united with the 
ophthalmic branch which the seventh cranial nerve in these animals sends into 
the orbit. This ophthalmic branch of the trigeminal is also described by Ewart 
for Lemargus and Raia, and, so far as I know, no attempt has been made to 
separate it from the fifth nerve as has been done for the ramus profundus. Ewart 
says that in Lemargus it rises sometimes from the fifth nerve trunk, sometimes 
from the mandibular division. In Raia the fifth nerve is described as dividing 
into maxillary and mandibular branches, and sending off a small superficial 
ophthalmic branch as well. This superficial ophthalmic branch of Elasmo- 
branchs may represent the frontal of mammals, and its small size in the former 
would correspond with the small size of the cerebrum in these animals compared 
with that of mammals, the protecting covering of which the frontal nerves supplies. 
If this is so, we have the fourth nerve in Elasmobranchs communicating with the 
frontal in exactly the same way as is found in the different stages of the human 
and rat embryos. 
In reptiles, on the other hand, Hoffmann has described the frontal as well as 
the nasal as arising from the ganglion ophthalmicum, and he mentions no commu- 
nication between the fourth and frontal nerves; and we must also note that the 
nerve which Strong* describes in amphibia, as arising from the partly segmented 
off, anterior end of the Gasserian ganglion, apparently represents the whole of 
the ophthalmic nerve. + 
The short preliminary account given by Chiarugif for the guinea-pig is not 
sufficient to show whether the nasal and frontal nerves are distinct at their origin 
in this animal. 
Ciliary Ganglion. 
We have seen that in Br;. (4 weeks) and in Ru. (5th week) no ganglion 
except the Gasserian was found in connection with the ophthalmic nerve. InC. R. 
(beginning of 6th week) however, a distinct ganglion was found in connection 
with the frontal branch of the ophthalmic. The cells of this ganglion are not in 
contact with the nasal nerve which lies at a lower level, although they are not far 
* « Cranial Nerves of Amphibia.” Journal of Morphology, vol. x., 1895. 
} The same appears to be the case in Ammoceetes Planeri. Kupffer. 
+ Monitore Zool. Ital. v. (1894). Noticed also in Journal of Royal Microscopical Society, October, 
1895, p. 507. 
