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66 ANAT03IY.

The Anterior or Malar Border is serrated for articulation with the
malar bone.
The Lateral Border is serrated, and bevelled above and below by the
projections of the outer plate and by the extension of the inner plate.
This border articulates with the squamous portion of the temporal
bone.
The Posterior Border (Fig. 23), somewhat concave in form, commences
at the body of the bone and terminates in the spinous process, the outer
Fig. 23.

Sphenoid Bone, posterior isurface.
portion beino; rough for articulation with the apex of the petrous portion
of the temporal bone. The internal portion of this border is smooth,
and forms the anterior boundary of" the middle lacerated foramen, and
is perforated by the posterior opening of the Vidian canal.
The Lesser Winr/s are two thin triangidar plates of compact bone ris-
ing by two pedicles from the anterior superior portion of the body. They
extend outwardly in the direction of the superior border of the greater
wings, and terminate in short points. The superior surface of the
lesser wing is smooth, being a continuation of the body of the bone, and
helps to form the base of the anterior fossa of the brain-case. The infe-
rior surface is part of the roof of the orbit, and forms the superior and
part of the internal boundary of the s])henoidal fissure (lacerated
foramen).
The ,Sj)liciioid((l Fissure is an opening approaching an isosceles triangle
in shape, the l)ase of the triangle being the body of the bone, the apex
extending outward to the notch in the superior border of the greater
wing. When the sphenoid bone is articulated with the frontal, this
fissure becomes the ant(>rior lacerated foramen, which transmits from
within outwardly the third, fourth, ophthalmic division of the fifth,
which breaks into three brauciies in this foramen, and the sixth nerve,
and from witliout iuwardly the o])htlialmic vein and a branch of the
lachrymal artery. The anterior border of the lesser wing is serrated for
articulation with the orbital plate of the frontal bone.
The Posterior Border of the lesser wing is short, and by its junction