Fig. 34.--_a_, notch forming the beginning of the lachrymal canal.
Fig. 35.--_a_, ridge for origin of the masseter muscle; _b_, frontal
process; _c_, zygomatic process.]
Near the middle of its cranial border it is notched obliquely by a
foramen (_a_), the beginning of the nasolachrymal canal.
=Malar Bone.= =Jugal Bone.= =Os zygomaticum= (Fig. 35).--The malar or
zygomatic bone is a flat curved plate of bone which forms the lateral
wall of the orbit and together with the zygomatic process of the
temporal forms the zygomatic arch. Its outer surface is smooth and
marked by a longitudinal ridge (_a_) for attachment of the masseter
muscle.
At its caudal end the bone is continued into two processes: one, the
=frontal= process or =orbital= process (_b_), is a triangular spine of
bone directed caudomediad; when the bones are articulated it lies
opposite the zygomatic process of the frontal to which it is joined by a
ligament (orbital ligament). The other, =zygomatic= process (_c_) of the
malar bone, extends ventrocaudad and articulates with a similar process
from the temporal to form the zygomatic arch above mentioned.
Its inner surface is smooth and looks into the orbit, except that of the
zygomatic process, which looks into the temporal fossa.
Its cranial border is roughened at the expense of both surfaces and
articulates with the maxillary bone. Its other borders are smooth except
the dorsal border of the zygomatic process, which is roughened for
attachment to the zygomatic process of the temporal.
=The Mandible.= =Mandibula= (Figs. 36 and 37).--The mandible (or
inferior maxillary bone) is composed of two halves which come together
at the cranial end and form the lower jaw. At its caudal end each half
articulates with the temporal bone at the mandibular fossa, and at its
cranial end it joins the opposite bone, the suture being known as the
=symphysis= of the jaw (=symphysis menti=) (Fig. 37, _a_).
Each half consists of a horizontal portion, the =body= (_b_), bearing
teeth on one of its borders (the =alveolar border=), and of a vertical
portion, the =ramus= (_c_).
The body (_b_) has the form of a flattened cylinder and has two surfaces
and two borders. The lateral surface (Fig. 36) is smooth and presents
near its cranial end a foramen (or sometimes two), the =mental foramen=
(_d_), forming the cranial termination of the mandibular canal. At its
caudal end is a deep fossa continuing on to the ramus, the =coronoid
fossa=, or =masseteric fossa= (_e_).
[Illustration: FIG. 36.--MANDIBLE, LATERAL SURFACE.