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BONES. 99
The Orbital Process is situated at the outer wall and floor of the
it is divided into two surfaces, the orbital and the temporal ; and
orbit :
two borders, the external and the internal.
The Orbital or Anterior Surface is smooth and concave, generally
presenting two grooves, which extend to near its anterior border, and
terminate in two foramina or canals for the passage of vessels and
.
nerves—one to the facial surface of the bone, and the other into the
temporal fossa. This surface, together with the great wing of the
sphenoid bone, forms the external wall and part of the floor of the
orbit.
The Temporal or Posterior Surface, in connection with the external
angular process of the frontal bone, forms the anterior boundary of the
temporal fossa. This surface is smooth and convex : it is pierced by a
foramen leading to the orbit.
The Maxillary Process is the strongest and thickest of the four : it
extends alono; the entire anterior border of the bone, formino; the articu-
lating portion of the zygomatic surface, and joining the malar process
of the superior maxilla.
The Zygomatic Process is situated at the posterior inferior portion of
the bone. It is broad and extends backward, its extremity being
bevelled at the extension of its lower part. It is rough and serrated,
and articulates Math the zygomatic process of the temporal bone, com-
pleting the zygomatic arch.
The Superior or Orbital Border is smooth and rounded, and presents
in outline an inverted arch. It forms a large portion of the outer
boundary of the orbit.
The Inferior or Zygomatic Border extends horizontally backward to
the zygomatic process, which, together with the lower border of the
zygomatic process of the temporal bone, forms the inferior border of
the zygomatic arch. This border is roughened for the origin of the
masseter muscle.
The Anterior Border is continuous with the articulating surface of
the maxillary process. The elevator muscle of the upper lip (levator
labii superioris proprius) arises just above the suture marking this
articulation, its point of origin extending slightly on to the external
surface of the bone.
The Posterior or Temporal Border is thin and curved somewhat like
an italic /. It faces backward, and is continuous above with the tem-
poral ridge, and below with the superior border of the zygomatic arch.
This border completes the circle enclosing the temporal region which
gives attachment to the temporal muscle.
The Sphenoidcd Border extends downward and inward from the
frontal process to the non-articulating notch, when it exists, at the l)ase
of the great wing of the sphenoid bone. This notch forms the anterior
boundary of the spheno-maxillary fissure. Occasionally the malar
bone does not enter into the formation of this fissure. When this
happens it is prevented from so doing by the articulation of the great
wing of the sphenoid with the superior maxilla, or by a small Wor-
mian bone. This border is serrated, and articulates with the great
wing of the sphenoid.