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BONES. 85
The Posterior or Zygomatic Surface is convex, and extends from the
root of the malar process inward and backward to its articulation with
the vertical plate of the palate bone.
The Superior Border is Mell defined, and is the dividing-line between
this and the orbital surfaces. The central portion of the border is
marked bv the infraorbital groove.
The Posterior Superior Angle is bevelled for articulation with the
orbital process of the palate bone.
The Tuberosity is a rounded eminence of bone just behind the posterior
inferior angle, back and above the wisdom tooth ; it is often so fragile
as to be broken away in extracting this tooth, the roots of which curve
upward, outward, and backward in it. The inner surface of the tuber-
osity is frequently roughened for articulation with the pyramidal pro-
cess of the palate bone. The tuberosity in the living bone is jjenetrated
by numbers of nutrient vessels. Midway between it and the zygomatic
surface are several larger apertures which lead into canals in the sub-
stance of the bone ; they are the posterior dental canals. One of them
passes into the substance of the bone, traverses the outer wall of the
maxillary sinus, and joins the anterior dental canal, which branches
from the infraorbital posterior to the infraorbital foramen. These
canals transmit the posterior dental vessels and nerves.
The Nasal Process is a thick irregular process of bone. Commencing
at the anterior superior angle of the facial surface of the bone, it extends
upward, inward, and backward, and forms part of the inner boundary
of the orbit and external surface of the nasal chambers. Its upper
extremity is serrated for articulation with the frontal bone in front
and the ethmoid bone behind, thus completing the anterior ethmoidal
cells. The anterior border is serrated for articulation with the nasal
bones.
The External Surface or Anterior Surface is marked by shallow
grooves, which are traces of the development and growth of the bone
downward. It is perforated by several foramina for the passage of
nutrient vessels to the substance of the bone. This surface gives origin
to the elevator muscle of the upper lip and of the wing of the nose
(levator labii superioris alseque nasi), the sphincter muscle of the orbit
(orbicularis palpebrarum), and the tendon of the eye (tendo oculi).
The Internal Surface of the Xasal Process is, for convenience of
description, all that portion of bone included between the superior
border and the floor of the anterior nares. This surface is marked by
two slightly concave portions of bone and two ridges. The lower ridge
articulates with the inferior turbinated bone, while the upper one articu-
lates with the middle turbinated bone.
The Inferior Meatus of the nose is bounded on the outside anteriorly
by the concave portion of bone below the inferior ridge. The Middle
Meatus is partly bounded externally by that concave portion betAveen
these ridges. The Superior Meatus at its commencement is similarly
bounded by that portion of this surface above the superior ridge.
The Malar Process is rough and triangular, and projects outward and
upward from the external surface of the body of the bone. It forms a
strong abutment immediately above the first molar tooth, and articulates