50S 



CHAP. XXI. 



VOICE AND SPEECH. 



AN important operation of muscular motion is in producing 

 sounds by means of those parts through which the air passes in 

 respiration. 



The vocal mechanism may be considered as consisting of lungs, 

 or bellows, capable of transmitting, by means of the connecting 

 windpipe, or trachea, a current of air passing through an appa- 

 ratus called the larynx, which is placed on the upper part of the 

 windpipe. This apparatus, though of very small dimensions, is 

 capable of producing sounds in great variation of pitch, quality, 

 and intensity, which are afterwards converted into the articu- 

 lations of speech by passing through a cavity consisting of the 

 pharynx, mouth, and nose. 



The larynx is the organ of voice. It consists of several carti- 

 lages united together by ligaments and articulations, and supplied 

 with a variety of muscles, by which they may be moved together 

 or separately, according to the modifications of the voice. 



E m C H, the thyroid cartilage ; 



H, its upper horn ; 



C, its lower horn, articulated to the cri- 



coid ; 



A n B C, the cricoid cartilage ; 

 A K, the crico-thyroideus muscle. 



