6
Diagram after Testut (modified), showing the posterior view of the larynx
with the muscles.]
On the top of the pyramid cartilages, in the folds of mucous membrane which
cover the whole inside of the larynx are two little pieces of yellow
elastic cartilage; and in the folds of mucous membrane uniting these
cartilages with the leaf-like lid cartilage (epiglottis) is a thin sheet of
muscle fibres which acts in conjunction with the fibres between the two
pyramid cartilages (_vide_ fig. 8). I must also direct especial attention
to a muscle belonging to the adductor group, which has another important
function especially related to vocalisation: it is sometimes called the
vocal muscle; it runs from the pyramid cartilage to the shield cartilage;
it apparently consists of two portions, an external, which acts with the
lateral ring-shield muscle and helps to approximate the vocal cords; and
another portion situated within the vocal cord itself, which by contracting
shortens the vocal cord and probably allows only the free edge to vibrate;
moreover, when not contracting, by virtue of the perfect elasticity of
muscle the whole thickness of the cord, including this vocal muscle, can be
stretched and thrown into vibration (_vide_ fig.
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