361. In the different parts of its course the windpipe is differently constructed, performs different offices, and receives different names according to the diversity of its structure and function. The first division of it is called the larynx (fig. CXXXV. 1.), the second the trachea (fig. CXXXV. 2), the third the bronchi (figs. CXXXV. 3, 4, 7, and CXXXVII.), and the fourth the air vesicles or cells (figs. CXXXV. 8, and CXXXVIII. 2). [Illustration: Fig. CXXXVI.—_Posterior View of the Larynx and Trachea._ 1. The os hyoides. 2. Thyroid cartilage. 3. Cricoid cartilage. 4. Arytenoid cartilages, separated from each other. 5. Epiglottis. 6. Opening of the glottis. 7. Termination of the cartilaginous rings of the trachea. 8. The ligamentous portion of the trachea. 9. Trachea laid open, showing its internal mucous surface and follicles, with the anterior portion of the cartilaginous rings appearing through it.] 362. The first portion of the windpipe called the larynx (figs. CXXXV. and CXXXVI), constitutes the organ of the voice. It is situated at the upper and fore part of the neck (fig. CLIII. 7, 9), immediately under the bone to which the root of the tongue, called the os hyoides (figs. CLIII. 6, and CXXXVI. 1), is attached. The larynx forms a very complex structure, and is composed of a variety of cartilages, muscles, ligaments, membranes, and mucous glands (fig. CXXXVI. 2, 3, 4, 5). At its upper part is a narrow opening of a triangular figure called the glottis (fig. CXXXVI. 6), by which air is admitted to and from the lung. Immediately above this opening is placed the cartilage, which obtains its name from its situation, _epiglottis_ (fig. CXXXVI. 5), which is attached to the root of the tongue (fig. CLIII. 6, 7), and which may be distinctly seen in the living body by pressing down the tongue.