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BONES. 133

maxillo-malar articulation, and below the foramen is situated the canine
fossa.
The Canine Fossa is above the alveolar process of the superior max-
illa, whicli supports the teeth.
Anterior Dental or Ilental Foramen is usually situated below a line
between the bicuspid teeth and above the external oblique line of the
inferior maxilla. This tbramen transmits the mental nerve and vessels.
The Supi^aorbital Notch or Foramen, the Infraorbital Foramen, and
the Anterior Dental Foramen are situated in a vertical line, one beneath
the other. They give exit to the terminal branches forming the three
divisions of the fifth or trifacial nerve, which transmits sensation from
the face.
The Orbital Cavities are two in number. They are situated
between the anterior portion of the brain-case and the superior portion
of the facial bones. They are irregular quadrilateral pyramids in shape,
their bases being directed forward and a little outward, and their apices
backward and a little inward. Their outer walls diverge from the median
line of the face at about an angle of forty-five degrees, while their inner
walls are nearly parallel with each other.
The roof of the orbit is concave, and formed by the horizontal or
orbital plate of the frontal bone and a portion of the lesser wing of the
sphenoid bone. The outer portion of the roof anteriorly is marked by
the laclirvmal fossa for the lodgment of the lachrymal gland. There
is also a depression at the inner portion of the roof anteriorly for the
attachment of the pulley of the superior oblique muscle.
The floor of the orbit is formed by the orbital surface of the superior
maxilla and the orbital processes of the malar and palate bones, the lat-
ter being situated at the posterior median angle.
At the inner third of this surface anteriorly will be found the open-
ing to the Lachrymal Canal. The depression just external to the lach-
rymal canal is for the origin of the inferior oblique muscle of the eye.
The outer wall of the orbit is formed by the anterior or orbital surface'
of the great wing of the sphenoid and part of the malar bone, its inter-
nal wall being formed by the nasal process of the superior maxilla, the
OS planum or orbital plate of the ethmoid bone, and the lachrymal bone,
making, in all, seven bones involved in the formation of the orbital
cavity. Three of these bones, however, the frontal, ethmoid, and sphe-
noid, enter into the formation of each orbit, so that it takes but eleven
bones to form the tw-o cavities.
The circumference of the orbit was described with the structures of
the face.
The apex of the orbit corresponds to the optic foramen.
There are ten openings into the orbit—viz. the optic, anterior lacerated,,
supraorbital, malar, and the anterior and posterior ethmoidal foramina,
the lachrymal and infraorbital canals, the spheno-maxillary fissure, and
the facial opening.
The Optic Foramen opens into the apex of the orbital cavity,
between the body and lesser M'ing of the sphenoid bone. It trans-
mits the optic nerve and the ophthalmic artery from the brain into
the orbit.