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BONES. 77
(cribritorm) plate unitin is ao-ain divided into the perpendicular plate and the crista galli.
The Perpendicufar Plate (Fig. 31) is a thin lamina of compact bone
situated in the median line between the two lateral masses. It extends
Fig. 31.

.f/ffiZ TZthmoidac^J^

Perpendicular Plate of Ethmoid (enlarged), shown by removing the right lateral mass.
downward and forward in the direction of the intermaxillary suture,
though it is frequently deflected to the one .side or the other. It forms
the upper third of the septum of the nose, and articulates posteriorly
with the cre.st of the sphenoid bone.
Borders.—The superior border of the perpendicular plate conjoins
the cribriform plate.
The Infei-ior Border is divided nearly in the centre into two portions.
The po.sterior inferior portion articulates with the vomer, while the
anterior inferior is roughened for the attachment of the nasal cartilage.
This cartilage is triangular in shape, and in the recent .state forms part
of the septum of the nose.
The Anterior Border articulates with the under surface of the na.sal
bones and also with the nasal spine of the frontal bone.
Grooves for Olfactory Nerves.—Immediately below the cribriform
plate, on the sides of the perpendicular plate, are fine grooves, running
downward, forward, and backward, in which are lodged the olfactory
nerves.
The Crista GaUi (named from its resemblance to a cock's comb in
shape) is an extension of the perpendicular plate above the horizontal
portion of the bone between the anterior fossae of the brain-case. It is
ivory-like in appearance.
The anterior border of the crista galli is vertical in direction and
grooved at its base. In the articulated skull this groove, joining a
similar one in the frontal bone just anterior to the internal frontal
crest, forms the so-called foramen cfficum.
The Ethmoidal Wings.—Extending outwardly from the base of the