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404 DENTAL ANATOMY.

three external surfaces, the facial, palatine, and orbital. The facial sur-
face, ^vliich is the largest of the three, is directed outward, and is irregu-
larly triangular in form, with the apex directed forward. The superior
border of this surface is considerably curved, and joins the premaxillary
in front and the nasal behind. The posterior border is irregular, and is
in contact from within outward with the frontal, lachrymal, and malar
bones respectively, being excluded by these bones from the rim of the
orbit. The inferior border is known as the dental or alveolar border,
on account of its affording support to the canine, premolar, and molar
teeth of the upper jaw. It is in contact with the premaxillary in front,
and terminates behind in a free extremity beneath the orbital fossa.
The surface thus bounded is uneven, being interrupted by elevations
and depressions. At the anterior angle the superior canine is implanted,
and the course of its powerful curved root is indicated by a well-marked
ridge or swelling of the external surface. Behind and above the pos-
terior termination of this is a broad, shallow depression, while behind
and below is another depression, the canine fossa, ending posteriorly in
a large foramen, the infraorbital foramen, situated above the interval
between the third and fourth premolars. Behind the infraorbital for-
amen a strong process is thrown up to meet the malar ; this is known
as the malar jyroccss of the maxillary. The posterior superior angle is
produced into a considerable rounded process, which passes as far back-
ward as the centre of the orbit to articulate with the frontal. This is
the nasal process of the maxillary, and is the homologue of a corre-
sponding process in the human skull bearing this name.
The posterior or orbital surface is relatively small, convex from before
backward, and concave from side to side. It is somewhat triangular in
shape, and forms the greater part of the floor of the orbit, being directed
upward and backward. It is bounded above and externally by the
malar, directly above by the lachrymal, and internally by the palatine
bones respectively, terminating in a free rounded border behind. The
internal portion of this last-mentioned border is separated from the
palatine by a notch, and forms a conspicuous eminence known as the
maxillary tuberosity. At the anterior extremity of this surface is seen
the posterior opening of the infraorbital canal, which traverses the max-
illary bone and serves for the transmission of the second division of the
trigeminal or fifth nerve, as well as a part of the external carotid artery,
which terminates in this situation as the infraorbital. This surface is
perforated by small foramina for the entrance of the su^jerior dental
nerves and arteries.
The inferior or palatal surface forms a considerable part of the bony
roof of the mouth as well as the floor of the nasal chamber. It is limited
in front by the premaxillary bone, externally by the free alveolar border,
posteriorly in part by the palatine and in part by a free edge, and inter-
nally by the suture with which it joins its fellow of the opposite side. It
is slightly concave from side to side, the alveolar border being consider-
ably elevated. Posteriorly it sends backward a narrow strip which ter-
minates in a free edge behind ; anterior to this, at a point opposite to the
anterior part of the sectorial, it widens rapidly. From this point
to its anterior termination it gradually narrows ai^ain. Just internal