30 Drxon—On the Development of the Branches of the Fifth Cranial Nerve in Man. 
eyeball. The lachrymal nerve is 1:3 mm. in length. No lachrymal gland 
was found. 
In Mr. the ciliary ganglion is a distinct collection of nuclei to the outer side 
of and behind the optic nerve. In section it presents an elongated figure, the 
long axis of which is vertical. Running forward through the extreme upper part 
of the ganglion is the nasal nerve, while fibres from the inferior division of the 
third nerve, which descends as it passes forwards, enter the ganglion from its 
inner side. From the ganglion some fine twigs run towards the eyeball both 
along the outer side of and below the optic nerve. The ciliary ganglion measures 
vertically 0°83 mm., from side to side 0°3 mm., and before backwards 0:2 mm. 
A fine nerve comes from the upper and inner part of the anterior end of 
Meckel’s ganglion in this embryo. This nerve turns upwards, and then outwards 
and a little forwards, and comes close to the ophthalmic artery and the optic 
nerve as these latter leave the cranium. This fine twig can be traced along the 
ophthalmic artery, and appears to end partly in the inferior division of the third 
nerve, and partly in the ciliary ganglion. 
Mr.—Frontal nerve, , p) 4omm: 
Supraorbital nerve, . ovOmm. 
Supratrochlear nerve, . 1°6mm. 
Nasal nerve, . : . 35mm. 
Infraorbital nerve, . . 13mm. 
Lachrymal nerve, . 5. old mam: 
In three out of these five embryos, namely C.R., F.M, and Mr., it is easy to 
determine what particular nerves of the adult are represented by the nerves found 
in the embryo. Further it will be noticed that already in the human embryo at 
the beginning of the sixth week all the important branches of the ophthalmic 
nerve of the adult are represented, viz. frontal, with its supraorbital and supra- 
trochlear branches; nasal, with its infratrochlear branch; and lachrymal. 
In comparing embryo Ru. (Sth week) with C.R. (beginning of 6th week) we 
are at once struck with the shortness of the frontal nerve in Ru. While the nasal 
nerve does not quite double its length in passing from the stage represented by 
Ru. to that of C.R., the frontal becomes more than ten times as long in C.R. as it 
isin Ru. It would seem that the nasal is the first formed branch of the ophthalmic, 
and that the frontal, which makes its appearance later, very soon overtakes it in 
length. That the frontal rather than the nasal is a direct continuation, as far as 
direction is concerned, of the main ophthalmic trunk in Rw. does not, as we shall 
see, make it unlikely that the nasal is the first representative of the ophthalmic 
nerve. A comparison of stage Br;. (4 weeks) with Ru. (5th week) supports the 
