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122 ANATOMY.
body of the sphenoid bone. They are convex and digitated over the
orbits, concave over the ethmoid bone, the crista galli projecting upward
from the centre of its cribriform plate. Just anterior to the crista galli
is situated the foramen csecum, the openings, including the cerebro-nasal
slit, for the olftictory and nasal nerves and vessels being fnmd on either
side of the projection. At the union of the lesser wings with the body
of the sphenoid bone the optic foramina are found. These foramina
transmit the optic nerves and ophthalmic arteries. The lesser wings and
a portion of the body of the sphenoid Ijone form the posterior boundary
of these fossae, the wings extending outwardly into the fissure of
Sylvius of the brain. The anterior fossa? support the frontal lobes
of the brain.
The Middle Fossce of the brain-case are formed by the great wings
and part of the body of the sphenoid bone, the squamous portion of
the temporal bone, and the anterior inferior portion of the parietal
bones. They are cup-shaped in form, and situated on a lower plane
than the anterior fossse. They are bounded in front by the lesser and
a portion of the greater wings of the sphenoid bone, behind l)y the
anterior surface of the petrous portion of the temporal bone, externally
by the squamous portion of the temporal bone and the anterior inferior
angle of the parietal bones, and internally by the body of the sphenoid
bone.
The Pituitary Fossa separates these fossse in the median line.
The middle fossse are digitated and their floors are pierced by numer-
ous openings. The anterior lacerated foramina, which are formed by the
approximation of the frontal bone and the body and two wings of the
sphenoid bone, open into these fossae anteriorly. Each of these foramina
transmits from within outwardly the third, fourth, and sixth, and the
ophthalmic division of the fifth cranial nerves. The ophthalmic vein and
a branch of the lachrymal artery pass through this foramen from with-
out inwardly. Just posterior to the anterior lacerated foramen, close to
the body of the bone, is the foramen rotundum. This transmits the
superior maxillary, the second division of the fifth nerve. Behind the
foramen rotundum, in the deepest portion of the fossa, is situated a
large oval foramen, the foramen ovale.. It gives passage from within
outwardly to the inferior maxillary or the third division of the fifth
cranial nerves, and from without inwardly to the lesser meningeal
artery.
External to the foramen ovale, and a little posterior to it, in the
spine of the great wing of the sphenoid bone, is situated the foramen
^jiinosuni. This foramen gives passage from without inwardly to the
middle meningeal artery.
Between the round and the oval foramina is sometimes located a
small foramen, the foramen A'^esali, for the transmission of a small vein
to the cavernous sinus.
Between the apex of the ])etrous portion of the temporal bone and
the bodv and posterior border of the great wing of the sphenoid bone
will be found the middle lacerated foramen (foramen lacerum medius).
In the recent state this foramen is filled up from below with fibrous
tissue. The carotid canal terminates at the apex of the petrous portion