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94 ANATOMY.

eighth week of embryonal life, Before birth the horizontal is longer
than the vertical plate.

The Inferior Turbinated Bone.

The inferior turbinated bones (maxillo-turbinal), two in number, are
situated at the lower third of each lateral wall of the nasal chamber.
Each bone forms the upper boundary of the inferior meatus of the
nose and the lower boundary of the middle meatus. It is thin and
frail, full of small foramina
Fig. 41. and minute canals. It is
scroll-like in form, curving
outward and downward. It
presents a body with two
surfaces, an internal and an
external ; two borders, supe-
rior and inferior ; and two
extremities, anterior and pos-
terior.
TJie Interned Surface (Fig.
Right Inferior Turbinated Bone, internal surface.
41) is convex from above
downward, and is marked by numerous foramina and longitudinal canals
for the passage of blood-vessels and nerves.
The External Surface (Fig. 42) is concave, smoother than the inter-
nal, excepting at its lower margin.
Fig- 42. where it is somewhat cellular in
structure and marked by numer-
ous foramina. It forms the roof
of the middle meatus of the nose.
TJte Superior Border is thin and
irregular, and is divided into three
portions, anterior, middle, and pos-
terior.
Eiglit Inferior Turbinated Hone, outer surface. The Anterior Portion articulates
with the inferior turbinated crest
on the internal surface of the nasal process of the superior maxilla.
The Middle Portion has arising from it three processes—the lachry-
mal, the ethmoidal, and the maxillary.
The Lachrymal Process runs ujiward and forward, and articulates
with tlie anterior inferior angle of the lachrymal bone. The outer por-
tion of this process is grooved and assists in forming the lachrymal canal.
The Ethmoidal Process arises just anterior to "the posterior third of
the superior border. It is broad, and extends upward to articulate with
the uncinate process of the ethmoid bone.
The Maxillary Process arises from the base of the ethmoidal process
externally, and curves outward and downward, forming a hook-like pro-
jection semicircular in shape. This process articulates with the inferior
border of the opening to the maxillary sinus.
The Posterior Portion of the sujierior border articulates with the
inferior turbinated crest of the palate bone.