FIFTH PAIR OF NERVES. 
281 
guments of the eyebrow and forehead : one 
of these branches, as described by Meckel, 
runs outward, through the orbicularis, toward 
the external canthus, and establishes anasto¬ 
moses with filaments of the facial portio dura 
nerve. The long branches are two, an external 
and an internal ; of those the external is, for 
the most part, the larger ; they ascend beneath 
the frontalis and the frontal aponeurosis, the 
former inclining outward, the latter inward, as 
they ascend ; they distribute in their course 
ramifications to the muscle, and to the deeper 
structures of the scalp, as well as some¬ 
times, according to Meckel, to the pericra¬ 
nium, and traversing the frontal aponeurosis, 
they become subcutaneous, and terminate in 
the structure and integument of the scalp. The 
external communicates with the superficial 
temporal nerves ; the internal with the internal 
frontal, the supra-trochlear. They are said both 
to anastomose with the branches of the sub- 
occipital nerve; but Meckel states that he 
has pursued them until they have escaped 
his sight, and yet he could not discover any 
anastomoses between them and the branches of 
that nerve. 
2. The nasal nerve is in size the second 
branch of the first division of the fifth, and arises 
always separately from the original trunk. Its 
course is inferior and internal to those of the 
other two, and hence the nerve is called by 
some the inferior, by others the internal branch. 
It is distributed partly to the eye and its appen¬ 
dages and partly to the nostril, and hence it is 
also called naso-ocular by Sœmmerring. The 
direction of its course is forward and very 
much inward ; it passes through the foramen 
lacerum into the orbit ; then traverses that re¬ 
gion from without inward toward its internal 
wall, and having reached it at the foramen or- 
bitarium internum anterius, it escapes from the 
orbit through that foramen, and passes into the 
cranium ; it emerges into the cranium from 
beneath the margin of the orbitar process of the 
frontal bone, and crosses the cribriform plate of 
the ethmoid obliquely forward and inward, 
contained in a channel in the bone, and in¬ 
vested by the dura mater, until it reaches the 
crista galli ; it then descends from the cranium 
into the nostril, through the cleft, which exists 
at either side of the crista galli at the anterior 
part of the cribriform plate, and having reached 
the roof of the nostril, it divides into its final 
branches.* 
The nasal branch is concealed at its origin 
by the frontal, which is situate external and 
superior to it. Before its entrance into the orbit 
it is placed by the outer side of and closely ap¬ 
plied to the third nerve. In entering the orbit 
* The nasal is usually described as terminating 
by dividing within the orbit into two branches, the 
ethmoidal or internal nasal, and the infra-trochlear or 
external nasal ; the author has preferred considering 
the former as the continuation of the nerve, be¬ 
cause in inferior animals both the nasal is the prin¬ 
cipal portion of the first division of the fifth, or 
alone constitutes it, and it is manifestly prolonged, 
as such, into the nostril and the beak. See Com¬ 
parative Distribution. 
it passes between the two posterior attachments 
of the external rectus muscle, in company with 
the third and sixth nerves, external to the 
former and between its two divisions, and 
internal and somewhat superior to the latter. 
In its course across the orbit the nasal nerve 
passes above the optic nerve, immersed in fat, 
and accompanied by the ophthalmic artery, 
being at the same time beneath the levator 
palpebræ, ihe superior oblique, and superior 
rectus muscles, and in crossing the optic 
nerve, it is placed between it and the last 
mentioned muscle. Through the foramen or- 
bitarium the nerve is accompanied by the an¬ 
terior ethmoidal artery, and within the cra¬ 
nium is situate beneath but not in contact 
with the olfactory bulb, being separated from 
it by the dura mater. The course of the nerve 
from the orbit to the nostril is liable to be 
modified by the developement of the frontal 
sinuses ; when they are very large, and extend, 
as they not unfrequently do, into the orbitar 
processes of the frontal bone and the horizontal 
plate of the ethmoid, the nerve may cross to 
the side of the crista galli without entering the 
cranium, being contained in a lamella of the 
ethmoidal bone. The nasal branch, before 
entering the orbit, receives, according to Bock, 
J. F. Meckel, and Cloquet, a filament from 
the sympathetic. The branches which the nasal 
gives off, are the lenticular, the ciliary, the 
infra-trochlear, and the nasal. 
The lenticular branch is given off as the nasal 
enters the orbit, and on the outer side of the 
optic nerve; it is a delicate branch, about half 
an inch long; it first anastomoses with the supe¬ 
rior division of the third nerve ; then runs for¬ 
ward along the outer side of the optic nerve, 
and terminates by joining the superior and pos¬ 
terior part of the lenticular ganglion. Accord¬ 
ing to Bock and Meckel junior, it occasionally 
gives off a ciliary nerve, and according to 
Meckel senior it is, in rare instances, derived 
from the third nerve. To the latter statement, 
however, the author hesitates to assent : it ap¬ 
pears to him, that it should rather be said in 
such cases to be wanting. 
The ophthalmic, lenticular or ciliary ganglion, 
according to Cloquet, is of an oblong form— 
its greater length from behind forward ; it is 
one of the smallest ganglia of the body, 
being, however, variable in size ; its colour is 
reddish, at times white ; it exists constantly in 
the human subject : it is situate between the 
external rectus muscle and the optic nerve, laid 
against the outer side of the nerve, at a little 
distance from its entrance into the orbit ; its 
external surface convex, corresponding to the 
muscle ; its internal, concave, to the nerve ; to 
its superior posterior angle is attached the len¬ 
ticular twig of the nasal branch of the first 
division of the fifth ; this filament constituting 
its long root ; to its inferior posterior angle a 
filament from the inferior division of the°third 
nerve is attached, constituting its short root. 
To the posterior part of the ganglion are also 
attached two filaments derived, one from the 
cavernous ganglion or the carotid plexus ; the 
other, the constant existence of which has not