lity in the movements of the neck
generally.

[Illustration: FIG. 20 (Spalteholz). Shows the thyroid cartilage above
and the cricoid below both viewed from the side. The anterior surface
is turned toward the right.]

[Illustration: FIG. 21 (Spalteholz). A front view of FIG. 20.]

[Illustration: FIG. 22 (Spalteholz). The back or signet surface of the
cricoid or ring cartilage, to which several muscles are attached.]

[Illustration: FIG. 23 (Spalteholz). The cricoid cartilage, seen from
the side, and showing behind and laterally the articular or joint
surfaces by which it connects with the thyroid below and the arytenoid
cartilage above.]

[Illustration: FIG. 24 (Spalteholz). Shows the arytenoid cartilages,
the most important of all the cartilages of the larynx, inasmuch as to
the part termed "vocal process" the vocal band is attached on each
side. The movements of the vocal bands are nearly all determined by
the movements of these cartilages, which have a swivel-like action. In
the above the front surfaces are turned toward each other.]

The _cricoid_ (_krikos_, a signet-ring) is the cartilage next in size.
It is situated below the thyroid cartilage, with which it is connected
by a membrane, the crico-thyroid. The wider part of this signet-ring
is situated behind, where it affords attachment to large muscles. It
also furnishes a base of support for two very important structures,
the _arytenoid_ (_arutaina_, a ladle) cartilages. As the vocal bands
are attached behind to them, and as they have a large degree of
mobility, they are from a physiological point of view the most
important of all the solid structures of the larynx.

There are two pairs of small bodies, the _cartilages of Santorini_, or
_cornicula laryngis_, surmounting the arytenoids, and the _cuneiform_,
or _cartilages of Wrisberg_, situated in the folds of mucous membrane
on each side of the arytenoids; but these structures are of little
importance.

The whole of the inner surface of the larynx is lined with mucous
membrane, though that covering over the true vocal bands is very thin,
and so does not cause them to appear red like the false vocal bands,
which are merely folds of the mucous membrane. However, the true vocal
bands may become red and thickened when inflamed, because of this same
mucous membrane, which, though ordinarily not visible to the eye,
becomes so when the condition referred to is present; for inflammation
is always attended by exc