THE LARYNX . 277 



most together and carry with them the vocal cords, 

 which are thus stretched tightly across the larynx. In 

 this position, they nearly close the air passage through 

 the trachea and are made to vibrate by the air as it 

 passes over their edges on its way from the lungs. These 



Vocal cor<fc Cricoid ? rti ' age ftbe vocal corJs 



FIG. 149. View of larynx from above, showing position of vocal cords. 



vibrations cause the air in the larynx to vibrate, and 

 its vibrations are directly transmitted by the air in the 

 throat and mouth to the external air. All the vibrations 

 of which the vocal cords are capable are of a rapidity 

 that comes within the range of the ear and they are 

 therefore perceived by us as sound. 



Volume. The loudness, or volume, of the sound pro- 

 duced by the vocal cords depends upon the force with 

 which the air of the lungs is pushed out between them. 

 A gentle voice is the result of very little pressure, 

 whereas a shout requires a sudden vigorous contraction 

 of the expiratory chest and abdominal muscles. 



