Drxon— On the Development of the Branches of the Fifth Cranial Nerve in Man, 37 
Before the appearance of Beard’s paper, Hoffmann* had described for reptiles 
the trigeminal ganglion, as being divided into two great masses which lie close 
together, but more or less distinct from one another. From the front ganglion 
the ophthalmic nerve arises, from the posterior one, the other two divisions of the 
fifth nerve. Hoffmann has no doubt but that this anterior ganglion in reptiles— 
the ganglion ophthalmicum as he calls it—is the homologue of a spinal ganglion 
(page 206). Hoffmann describes not only the nasal, but also the frontal, nerve as 
a branch or outgrowth of the ophthalmic ganglion (mesocephalic of Beard). In 
this way then reptiles seem to differ from Elasmobranchs, since in the latter the 
nasal alone arises from the separate ganglion. Hoffmann further brings out the 
important fact that the nasal nerve is at first larger than the frontal in reptiles. 
In the forms studied by Beard, Van Wijhe, and others, the mesocephalic 
ganglion and its roots, soon become fused with the Gasserian ganglion and the 
roots of the fifth nerve. From the very first, the distance between the two is 
very short. The result of this fusion is that the ramus profundus then appears to 
be a branch of the trigeminal nerve. 
Ewartt has given an account of these nerves in the adult in certain Elasmo- 
branch fishes. 
In Lemargus he finds that the ophthalmicus profundus possesses a root, a root 
ganglion, and a trunk which gives off a number of well-marked branches. The 
nerve takes origin from the side of the medulla, immediately in front of the fifth 
nerve, and at first is partly blended with the fifth. Outside the cranial wall a 
special ganglion is present on the nerve—the mesocephalic of Beard—which lies 
dorsal to, but only a slight way in front of, the Gasserian ganglion. From this 
ganglion a nerve passes forwards, having the same relations to the ocular muscles 
as the nasal presents in man. 
In Raia the ganglion of the ramus profundus lies some distance in front of 
the Gasserian ganglion, and nearer to the third nerve than in Lemargus. 
In Torpedo,t on the other hand, the ganglion of the ramus profundus lies in 
close contact with the Gasserian. This author also states in another place§ that 
in Elasmobranchs the ramus profundus, which evidently represents the nasal 
nerve in man, is neither a branch of the third nerve nor of the trigeminal. The 
ramus profundus belongs to a ganglion called by him the profundus or oculo- 
nasal ganglion, which is identical with the mesocephalic ganglion of Beard. 
* “ Weitere Untersuchungen zur Entwicklungsgeschichte der Reptilien,’’ Morphologisches Jahrbuch, 
1886, Bd. xi., p. 202. ; 
+ ‘© On the Cranial Nerves of Elasmobranch Fishes,” Proceedings of the Royal Society, 1889, vol. xlv., 
p. 524. 
t ‘‘On the Cranial Nerves of Torpedo,” Proceedings of the Royal Society, 1890, vol. xlvii., p. 290. 
§ ‘‘On the Development of the Ciliary or Motor Oculi Ganglion,” Proceedings of the Royal Society, 
1889, vol. xlvil., p. 287. 
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