Page:Popular Science Monthly Volume 9.djvu/412

388 the V turned forward. In women it is less prominent than in men, and it is known as Adam's apple. The lateral cartilages, which spring from the ring-cartilage at the back of the larynx, assume the form of little triangular pyramids with uneven surface. They are slightly curved toward the upper extremity, and support a little horny plate, which in the eyes of the ancient anatomists resembled the snout of a pitcher. The lateral cartilages, being very mobile, play an important part in the emission of the voice.

The larynx is to some extent movable. Being attached to the hyoid or tongue bone by means of a membrane strengthened by ligaments, it is lifted up by the action of muscles extending from the tongue-bone to the external surface of the thyroid cartilage; it is pulled down by the action of muscles which extend from this same cartilage to the sternum. Further, the vocal apparatus is affected by the movements of the pharynx and of the tongue, as also by the respiratory movements. The solid parts of the larynx, being more or less movable, change position under the action of muscles which pass from one to another of them. Bundles of muscular fibre which spring from the annular cartilage (the cricoid) cause the thyroid cartilage to move up and down, and this movement produces tension of the vocal cords. Muscles springing from the cricoid and from the thyroid produce a rotation of the lateral cartilages, and modify the conditions of the cords. Finally, there are bundles of muscular fibre extending from one lateral cartilage to the other; when these contract, the walls of the larynx are brought nearer to each other, and the opening through which the air passes is made narrower.

Internally, the larynx is lined with mucous membrane, which is continuous with the mucous membrane of the mouth. Two pairs of ligaments, extending from the thyroid to the arytenoid, divide the cavity into compartments. The lower portion is limited by an arch formed of thick folds of mucous membrane. The middle portion is distinguished by the presence of folds supported by ligaments. These are the vocal cords, which play the principal part in the act of phonation. The superior cords, which resemble thin bands, occupy both sides. The inferior cords, or true vocal cords, which are very thick, are situated beneath the upper, and extend considerably beyond them toward the median line. They bound the orifice called the glottis. This orifice, which in the state of repose is triangular in shape, varies constantly in form and in dimensions under the influence of respiration and the emission of the voice. This use of the term glottis, which signifies tongue, to designate an orifice, is very curious, and is