The _epiglottis_ is fixed at the anterior portion of the larynx, at the root of the tongue, within the angle formed by the two surfaces of the thyroid cartilage. It is a very elastic fibro-cartilage, freely moving in a posterior direction. Its color is yellowish and its general form that of a spoon; its upper surface is covered with a multitude of little mucous glands set in shallow cavities. In the downward passage of food the _epiglottis_ covers the upper orifice of the larynx like a valve, over which the food passes into the œsophagus or gullet, without being able to enter the larynx and the trachea. In the centre of its interior side there is a little rounded cartilage, movable in every direction, which has as yet no name. Czermak mentions it first in his observations with the laryngoscope. In the male larynx, after the voice has altered, the cartilages become more or less ossified and gradually harden with increasing age. The cartilages of the female larynx, with rare exceptions, usually continue with little or no change. The muscles, by which the movements of the larynx are effected, are:
I. The posterior crico-arytenoid. II. The lateral crico-arytenoid. III. The crico-arytenoid. IV. The thyro-arytenoid. V. The arytenoid. VI. The internal thyro-arytenoid.
In late works upon laryngoscopy the different muscles of the larynx are variously designated and divided. Bataille terms the first three of the above-named muscles the exterior muscles of the larynx; the three others he comprehends under the name of thyro-arytenoid or vocal muscle, which divides into three slips in the interior of the larynx. This, however, as well as the description of the character and action of the different muscles, belongs to the department of science. What I have already stated seems to me to be sufficient for an understanding of the action of these organs in the production of sound in the different registers. The reader is referred to any good manual of anatomy for a full description of the muscles, ligaments, nerves, vessels and membranes.
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