NERVOUS SYSTEM., 123 
bably the motor root; while the larger and ganglionic, and with 
coarser fibres, is devoted to sensation. 
Peculiarities aud Course of the Fifth Pair .—I will not now 
minutely follow the course of the fifth pair,—I shall have to speak 
of this when describing the different parts of the face; but I 
must slightly glance at this portion of our subject. Here, in har¬ 
mony with what we have already seen, we are first struck with 
the increased bulk of the trigeminus in all our patients, with re¬ 
gard to both roots of it, and more particularly the motor root. 
It has far more to do in the quadruped than in the human being. 
It has to give power of motion to the jaws, which are not only 
the agents of mastication, but, in many animals, the weapons of 
offence : it has to bestow additional sensibility on the lips, which 
in all of them to a certain degree, and in some of them to a re¬ 
markable extent, are to supply the place of hands, not only by 
executing every prehensile function,but being, as it were, the pecu¬ 
liar seat of the organ of touch. The fifth pair of nerves exert also 
a peculiar influence over the organs of sense, of which we shall 
have numerous instances, sometimes very interesting, and at 
other times not a little mysterious; and which influence will ne¬ 
cessarily increase the acuteness of that sense, greater by far 
in the quadruped than in man, and therefore requiring greater 
development of the nerves. 
Division of the Nerve. —After the ganglion has been formed 
by the greater root, and the ganglionless part has joined the other, 
and a perfect but evidently compound nerve has been the result, 
the trigeminus very curiously divides into three parts, within the 
cavernous sinus ; and each, before it quits the cranium, assumes 
to itself a distinct investment of dura mater. These divisions 
or branches are called, from the parts to which they are destined, 
—the ophthalmic , the anterior (superior), and the posterior 
(inferior) maxillary nerves. I shall give an exceedingly short, 
perhaps unsatisfactory, sketch of them. If, amidst the multi¬ 
plicity of subjects which these lectures embrace, any are neg¬ 
lected, they must be those of pure anatomy. 
The Ophthalmic Nerve. —This is the smallest of the three. It 
is found within the sinus in conjunction with the superior max¬ 
illary, which it soon leaves, and passes through the foramen la- 
cerum into the orbit; there it subdivides and forms three dis¬ 
tinct branches,— the supra-orbital (the frontal), the lachrymal, 
and the lateral nasal (the nasal). The supra-orbital climbs be¬ 
hind the muscles of the eye, giving some filaments to the rectus 
superior and to the superior oblique, and some to the fatty mat¬ 
ter of the eye; and the main branch, escaping through the su¬ 
perciliary foramen, is soon lost in ramifications on the elevator of 
