the false vocal bands above and the true
vocal bands below is termed the _ventricle of the larynx_. It allows
of more space for the free movements of the bands, especially those
more important in voice-production.

The vocal bands are attached behind to the projecting angle of the
base of the arytenoid cartilage, which is itself somewhat triangular
in shape, the base of the triangle being downward and resting on the
upper and posterior (back) surface of the cricoid cartilage, with
which it makes a free joint, so that it can move swivel-like in all
directions. This is most important, because through it is explained
the fact that the vocal bands may be either tensed and lengthened or
relaxed and shortened.

_The muscles act on these movable cartilages, and nearly all the
changes in the vocal bands are brought about through the alterations
in position of the arytenoid cartilages, to which they are attached
behind._

Before describing the muscles of the larynx, the reader is reminded of
the order of structures from above downward, in front, which is as
follows:

The hyoid bone.
The thyro-hyoid membrane.
The thyroid cartilage.
The crico-thyroid membrane.
The cricoid cartilage.
The trachea.

The latter is connected with the cricoid cartilage by its membrane.

All the above structures can be felt in one's own person, the more
readily if he be thin and have a long neck. The hyoid bone, or
tongue-bone, is that hard structure just above the cricoid cartilage,
and which one may easily demonstrate to be much more movable than the
larynx itself. The tongue muscles are attached to it above, and from
it, below, the larynx is suspended, as already explained.

The muscles of the larynx are best understood if the principle of
antagonistic action already referred to be remembered. Speaking
generally, the muscles are arranged _in pairs_ which have an opposite
or antagonistic action--viz.: (1) Those that open and close the
glottis; (2) those that regulate the tension, or degree of tightness,
of the vocal bands.

1. The muscles whose action tends to approximate the vocal bands--the
_adductors_--are the _arytenoid[=e]us proprius_ and the
_thyro-arytenoid[=e]us_. The former is attached to the posterior or
back surface of both arytenoid cartilages; the latter, as its name
indicates, to the anterior and inner surface of the thyroid and the
anterior lower surface or angle (_vocal process_) of the aryten