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286 ANATOMY.

tympani, thus controlling the act of mastication and to some extent
deglutition and hearing. Fibres of the fifth nerve aftbi'd general sensa-
tion to the entire skin of the head and face, except in the occipital
region and the back and lower part of the ear, also to the mucous mem-
branes of the mouth, with the exception of the posterior pillar of the
fauces and the posterior third of the tongue, which derive their sensa-
tion by means of the glosso-pharvngeal nerves (Ranney).
The Ophthaliaic, or first division of the fifth nerve, is the smallest
of the three cords, being but about an inch in length. The table on
page 287 will show^ that it is derived wholly from the sensory root. Its
function is to impart sensation to the eyeball, the lachrymal gland, the
mucous lining of the eye, and a portion of the nose and of the eye-
brow and forehead. It commences from the upper, inner, and anterior
portion of the margin of the Gasserian ganglion. It is a flattened cord,
and passes forward along the outer wall of the cavernous sinus, and
terminates before or just as it is about to pass through the anterior
lacerated foramen by dividing into three main branches, the frontal,
lachrymal, and nasal.
Brandies of the OpJithdhiiic Nerve.—
Those within the cavernous sinus. Lachrymal,
Frontal, Nasal.
The ophthalmic nerve gives off two small branches within the cav-
ernous sinus.
The Frontdl Nerve is the largest of the branches given off by the
ophthalmic, and is in reality its axial continuation. It enters the orbit
through the most superior portion of the anterior lacerated foramen,
and passes forward in the median line above the muscles and below the
periosteum. It terminates midway between the apex and base of the
orbital cavity, above the levator palpebrte snperioris muscle, by dividing
into two branches of unequal size, the su])ratrochlear and the supra-
orbital.
The Suprafrorhkfir Nerve is nnich the smaller of the two terminal
branches of the frontal. It extends obliquely inward and forward over
the trochlear muscle, passing out of the orbit, and curves around the
supraorbital arch between the supraorbital foramen and the trochlear fossa.
It then extends beneath the corrugator sujicrcilii and frontalis muscles,
and divides into two terminal branches. These branches pierce the
orbicularis and frontalis muscles, supplying them as well as the integ-
ument ; also the lower and median portion of the forehead, interlacing
with the corresponding nerve of the o])posite side. This nerve also
gives off two distributing branches, one extending from the nerve near
the trochlear nuiscle, which passes downward and joins the infratrochlear
branch of the nasal nerve, and the other near its exit from the orbit,
which passes to the eyelid and bridge of the nose.
The >Supraorhitaf Nerve is really a continuation of the frontal. It
passes forward, and emerges from the orbit through the supraorbital
notch or foramen. It then curves upward on the forehead, and divides
into a median and a lateral l)ranch, which ])ierce the muscles and become
the cutaneous nerves. Its branches of distribution are several small
cords which descend to the struc^tures of the upper eyelid, and one