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BLOOD-VESSEL SYSTEM OF THE HEAD, ETC. 241

which enters a small foramen often seen within the supraorbital foramen
or notch.
Tlie Palpebral Arteries are two in number, superior and inferior.
They usually arise together from the ophthalmic, nearly opposite the
pulley of the superior oblique muscle. From this point they diverge,
the sui>erior branch passing above, the inferior below, the internal tarsal
ligament. They distribute small branches to the conjunctiva and the
lachrymal caruncle and sac. They then pass outward between the
orbicularis palpebrarum muscle and the trochlea, and encircle the eye-
lids near their free margins. They anastomose with branches of the
lachrymal as well as with the orbital branches of the temporal and
infraorbital arteries. A branch from the palpebral artery generally
accompanies the nasal duct into the nasal chamber.
The Frontal Artery is one of the terminal divisions of the ophthal-
mic, and arises in close proximity to the trochlear process or notch on
the frontal bone. It passes out of the orbital cavity, curves around
the internal angular process of the frontal bone or inner extremity of
the supraorbital arch, and is distributed to the superior lid of the eye,
integument, muscles, and pericranium of the forehead, as well as to the
nasal slip of the frontal muscle. It auastomoses with its fellow of the
opposite side and with the supraorbital artery.
The External Nasal Artery is the other terminal division of the
ophthalmic. It arises close to the trochlear process or notch on the
frontal bone, and passes forward over the internal tendo palpebrarum
and through the orbicularis palpebrarum muscle. It then extends down-
ward along the root of the nose, and communicates with the angular and
nasal arteries, branches of the facial. Occasionally it communicates by
a small branch with the artery of the opposite side, or it may pass down
the nose and anastomose with the anterior nasal artery, a branch of the
anterior ethmoidal. In its course it gives off branchlets to the lachrymal
sac, canal, and caruncle and the orbicularis palpebrarum muscle.
Variations.—The lachiymal artery may arise directly from the middle
meningeal. When it so arises it passes out of the brain-case through,
the notch in the border of the anterior lacerated foramen, and gives off
a small recurrent branch, which communicates with the lachrymal and
middle meningeal arteries, and again becomes part of the main trunk
of the lachrymal. Occasionally the major portion, or even all, of the
blood-supply of the lachrymal artery comes through this source, "Where
the facial artery is small or altogether wanting the nasal artery is of
large size and supplies its place. The terminal branches of the oph-
thalmic artery have a large and varied communication with other
arteries in this region, such as its fellow of the opposite side, the facial,,
infraorbital, transverse facial, temporal, middle meningeal, ethmoidal,,
and the spheno-palatine.

The Cerebral Arteries.
The Cerebral Arteries, branches of the internal carotid, are two in
number, anterior and posterior, the posterior cerebral artery being a
branch of the basilar.
Vol. I.—16