Page 54 - My FlipBook

64 ANAT03IY.

the one side or the other, making tlie sinuses of unequal size. Other
incomplete septa may be seen at the posterior portion of these cavities,
which divide them into several compartments. Sometimes they extend
back and penetrate the basilar process of the occipital bone. They are
lined by mucous membrane, which is continuous with that of the nasal
cavity. The larger part of the anterior surface of the body is formed
by the sphenoidal turbinated or spongy bones; they are triangular in
shape, their apices pointing downward and backward, their upper mar-
gins being some^yhat deflected, which opens a passage or communication
between the sinuses and the nose. They are formed from separate
points of ossification, but soon unite with the sphenoid behind and the
ethmoid in front.
The Inferior Surface (Fig. 22) is apparently a continuation of the
anterior. It presents in the middle line a triangular spine, the ros-

LAXATOD TYMPANI

JUdtnulua' /iTOCest -
Sphenoid Bone, anterior surface. (In this figure both the anterior and inferior surfaces of the
body of tlie sphenoid bone are shown, the bone being held with the pterygoid jirocesses almost
horizontal.)
trum, which is a continuation of the vertical lamina of the bone of the
anterior surface, and articulates with the fissure formed by the alse of
the vomer. These alse, together Avith the vaginal process of the sjihe-
noid, \vhich are prolongations of the internal pterygoid plates, cover
the greater part of the inferior surface of the body of the bone, and
lock the parts together.
The Greater Wings are two irregular strong processes of bone
arising from the lateral surflices of the body. Thev extend outMard,
forward, upward, and backward, and jM'esent for examination three sur-
faces, the internal, external, and orbital; and five borders, the superior,
inferior, anterior, lateral, and posterior.
The Internal or Cerebral Surface is situated entirely within the
brain-case, and forms part of the middle fossa of the cranium. This
surface is deeply concave, and marked by eminences and depressions