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BONES. 65
for the convolutions of the brain. At the point where the win^
joins the body of the bone anteriorly is a round opening, the foramen
rotundum, which transmits the second division of the fifth nerve.
About half an inch posterior to this may be seen an oval aperture
larger than the preceding. This is called the foramen ovale, and
transmits the third division of the lifitli and the small petrosal nerves
from within outwardly, and the lesser meningeal artery from without
inwardly. Behind and a little external to the former, in the spinous
process of the bone, is a small aperture, the foramen spinosum, for the
transmission of the middle meningeal artery.
The External iyTemporo-zygomatic) /Surface is convex from above
downward, and is divided into two portions, a superior and an
inferior, by a ridge of bone, the infratemporal crest. The superior
portion is the larger of the two, averaging about half an inch in
width and an inch and a half in height. This is concave, forms part
of the temporal fossa, and gives attachment to part of the temporal
muscle. The inferior portion is also concave, enters into the formation
of the zygomatic fossa, and gives attachment to the outer part of the
external pterygoid muscle. The posterior border of this portion of the
bone extends downward and outward, and terminates externally in a
point of bone called the spinous process, wJiich gives attachment to
the internal lateral ligament of the lower jaw and the laxator tympani
muscle.
The Orbital Surface, or that portion of the greater wing which
assists in forming the outer wall of the orbit, is smooth, and may be
divided for purposes of description into two portions, an outer and an
imier, by an imaginary line drawn from the notch found in its superior
border, for the accommodation of a branch of the lachrymal artery to
a point just external to the foramen rotundum. The outer portion is
quadrilateral in form, while the inner, or that immediately above the
pterygoid process, is triangular.
The Quadrilateral or Outer Portion is composed principally of
spongy tissue, though that which joins the malar bone is compact
and helps to form the orbito-temporal partition. This surface articu-
lates above with the frontal bone, externally with the malar bone, and
inforiorly it forms the posterior boundary of the spheno-maxillary fis-
sure. The inner portion is thin, being made up of compact tissue. The
superior border forms the posterior boundary of the sphenoidal fissure.
Just below this border, on the inner surface, near the imaginary line
dividing the orbital surface, there is generally found a small spine of
bone, for the origin of part of the lower head of the external rectus
muscle.
Borders.— The Superior Border is divided into two jiortions, an
outer and an inner ; the outer is broad, triangular, and roughened, the
greater part being for articulation with the frontal, the remainder with
the parietal bone. The inner portion is thin, and forms the outer
boundary and anterior superior angle of the sphenoidal fissure or
anterior lacerated foramen.
The Inferior Border is smooth, rounded, and forms the posterior
l)oundary of the spheno-maxillary fissure.
Vol. I.—
BONES. 65
for the convolutions of the brain. At the point where the win^
joins the body of the bone anteriorly is a round opening, the foramen
rotundum, which transmits the second division of the fifth nerve.
About half an inch posterior to this may be seen an oval aperture
larger than the preceding. This is called the foramen ovale, and
transmits the third division of the lifitli and the small petrosal nerves
from within outwardly, and the lesser meningeal artery from without
inwardly. Behind and a little external to the former, in the spinous
process of the bone, is a small aperture, the foramen spinosum, for the
transmission of the middle meningeal artery.
The External iyTemporo-zygomatic) /Surface is convex from above
downward, and is divided into two portions, a superior and an
inferior, by a ridge of bone, the infratemporal crest. The superior
portion is the larger of the two, averaging about half an inch in
width and an inch and a half in height. This is concave, forms part
of the temporal fossa, and gives attachment to part of the temporal
muscle. The inferior portion is also concave, enters into the formation
of the zygomatic fossa, and gives attachment to the outer part of the
external pterygoid muscle. The posterior border of this portion of the
bone extends downward and outward, and terminates externally in a
point of bone called the spinous process, wJiich gives attachment to
the internal lateral ligament of the lower jaw and the laxator tympani
muscle.
The Orbital Surface, or that portion of the greater wing which
assists in forming the outer wall of the orbit, is smooth, and may be
divided for purposes of description into two portions, an outer and an
imier, by an imaginary line drawn from the notch found in its superior
border, for the accommodation of a branch of the lachrymal artery to
a point just external to the foramen rotundum. The outer portion is
quadrilateral in form, while the inner, or that immediately above the
pterygoid process, is triangular.
The Quadrilateral or Outer Portion is composed principally of
spongy tissue, though that which joins the malar bone is compact
and helps to form the orbito-temporal partition. This surface articu-
lates above with the frontal bone, externally with the malar bone, and
inforiorly it forms the posterior boundary of the spheno-maxillary fis-
sure. The inner portion is thin, being made up of compact tissue. The
superior border forms the posterior boundary of the sphenoidal fissure.
Just below this border, on the inner surface, near the imaginary line
dividing the orbital surface, there is generally found a small spine of
bone, for the origin of part of the lower head of the external rectus
muscle.
Borders.— The Superior Border is divided into two jiortions, an
outer and an inner ; the outer is broad, triangular, and roughened, the
greater part being for articulation with the frontal, the remainder with
the parietal bone. The inner portion is thin, and forms the outer
boundary and anterior superior angle of the sphenoidal fissure or
anterior lacerated foramen.
The Inferior Border is smooth, rounded, and forms the posterior
l)oundary of the spheno-maxillary fissure.
Vol. I.—
