CHAPTER XV 

 A STUDY OF THE VOICE AND OF SPEECH 



The Vocal Organs of Man. Articulate speech is one of the 

 most distinguishing characteristics of mankind indeed, 

 we may say that man is the only animal that talks. As we 

 might expect, a rather delicate and complicated mechanism 

 is necessary for the production of all these various sounds. 

 This consists of three parts : namely, the lungs, which serve 

 as an air bellows ; the vibrating membranes known as the 

 vo'cal cords (Latin vox, vocis = voice) ; and the resonating 

 chambers of the throat, nose, and mouth chambers. We 

 have already discussed (p. 213) the structure and action of 

 the lungs. We shall now proceed to a description of the 

 voice box or lar'ynx, which contains and regulates the vocal 

 cords. 



The Cartilages of the Larynx. 1 In our study of the air 

 passages leading to the lungs, we learned that the windpipe 

 is kept open by the C-shaped bands of cartilage, which we 

 can feel on the ventral surface of the neck region. Crowning 

 the windpipe and opening into the throat cavity is the larynx, 

 the walls of which are composed of movable pieces of carti- 

 lage. The largest of these is the thy'roid (Greek = shield- 

 shaped), which can be felt on the ventral surface of the larynx 

 or "Adam's apple." The two halves of the thyroid are 

 partly united on the ventral surface, curve around the sides, 

 but leave a considerable opening dorsally. Each half sends 



1 Most of the structures described in this and the following section 

 can be demonstrated to the class by using the windpipe and larynx of 

 a sheep. 



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