3. Speech is intimately related to the sense of hearing. A child born deaf is, of necessity, dumb also; not because the organs of speech are imperfect, for he can utter cries and may be taught to speak, and even to converse in a rude and harsh kind of language; but because he can form no accurate notion of sound. And a person, whose hearing is not delicate, or as it is commonly expressed, who "has no ear for music," cannot sing correctly. A person who has impaired hearing commonly talks in an unnaturally loud and monotonous voice. These examples show the necessary relation of intelligence and the sense of hearing with that form of articulate voice, which is termed speech. [Sidenote: 4. Organ of the voice? Where situated? Of what is its framework composed?] 4. THE ORGAN OF THE VOICE.--The essential organ of the voice is the Larynx. This has been previously alluded to in its relation to the function of respiration; and, in the chapter on that subject, are figured the front view of that organ (Fig. 35), and its connection with the trachea, tongue, and other neighboring parts (Fig. 38). It is situated at the upper part of the neck, at the top of the trachea, or tube by which air passes into and out of the lungs. The framework of the larynx is composed of four cartilages, which render it at once very strong and sufficiently flexible to enable it to move according to the requirements of the voice. {229} [Illustration: FIG. 55. SECTION OF THE LARYNX AND TRACHEA. A, The Epiglottis. B, The Thyroid Cartilage. C, Arytenoid Cartilage. D, Ventricle of the Larynx. E, Cricoid Cartilage. F, Right Vocal Cord. H, The Trachea.] [Sidenote: 5. Names, formation, and situation of the cartilages?] 5. The names of the cartilages are (1) the _thyroid_, which is a broad thin plate, bent in the middle and placed in the central line of the front part of the neck, where it is known as the _pomum Adami_, or Adam's apple (Fig. 55, B), and where it may be felt moving up and down with each act of swallowing; (2) the _cricoid_, which is shaped like a seal ring, with the broad part placed posteriorly (Fig. 55, E). At the top of the cricoid cartilage are situated the two small _arytenoid_ cartilages, the right one of which is shown in Fig. 55, C. These latter little organs are much more movable than the other two, and are very important in the production of the voice. They have a true ball and socket joint, and several small muscles which contract and relax with as perfect regularity and accuracy as any of the larger muscles of the body. [Sidenote: 6. Lining of the interior of the larynx? The epiglottis?]