Of the _epiglottis_, a flexible cartilage, it is necessary to say little, as its function in voice-production, if it have any, has never been determined. It hangs as a flexible protective lid over the glottis, and food in being swallowed passes over and about it. It no doubt acts to keep food and drink out of the larynx, yet in its absence, in some cases, owing to disease, no very great difficulty was experienced, probably because certain muscles acted more vigorously than usual and tended to close up the glottic chink. The following simple diagram will, it is hoped, make the relative position of parts plain so far as the anterior (front) attachments of parts to the thyroid cartilage are concerned. It will be understood that the inner anterior surface is meant, and that by "middle line" is intended the middle line of the body, the imaginary vertical diameter passing like a plumb-line from the middle plane of the head, let us suppose, downward just in front of the larynx. [Illustration: FIG. 29.] The angle made above and in front where the two wings of the thyroid cartilage meet is termed _Adam's apple_ (_Pomum Adami_), and in some cases, mostly males, is very prominent. Adam's apple has in itself, however, no special significance in voice-production. The little concavity between 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.