Above the œsophagus, immediately over the palate, lie close together, and separated only by a very thin osseous partition, the two posterior nasal orifices. These serve as passages for the air during inspiration and expiration; they are likewise considered as belonging to the resonance apparatus. Upon both sides of the cavity of the mouth, between the two wings of the palate, lie the tonsils, two glandular bodies, which separate the sides of the cavity of the mouth from the _pharynx_. The anterior cavity of the mouth, which is separated from the nasal cavities by the palate, requires no description, as every one can acquaint himself with its structure in his own person and in others. Upon its formation, as well as upon the position of its different parts and upon the character of those parts of the larynx and of the cavity of the mouth which have been described as the resonance apparatus, the difference in the fulness and timbre of tones depends. 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.