VOICE AND SPEECH. 



569 



shaped opening in the glottis. On the other hand, during the pro- 

 duction of vocal sounds the triangular posterior opening is com- 

 pletely ,closed, while the anterior portion of the rima glottidis 

 becomes a very fine fissure, or slit. 



mi 



ito 



vocal 



Fig. 212. The Posterior Rhinoscopic Image. (BOSWORTH.) 



VOICE. 



It is the vibration of the edges of this fissure by the passage of 

 through it that produces sound: the voice. The air expelled 

 the lungs acquires a maximum of tension in the narrow tracheal 

 causing it to strike under the true vocal cords and put them 



the proper vibrations. But the tone produced will not always 

 the same caliber and height, since the expired air may find the 

 cords in different states, the result of muscular contractions. 



The Height of the sound produced in the larynx depends upon 



number of vibrations of the vocal cords during a given time. 



