356 COORDINATION AND SENSATION 



ance, are two other folds of membrane, called the false 

 vocal cords (B, Fig. 149). The false cords do not produce 

 sound, but they aid in the closing of the glottis. 



How the Voice is Produced. The voice is produced 

 through the vibrations of the vocal cords. A special set 

 of muscles draws the arytenoid cartilages toward each 

 other, thereby bringing their edges very near and parallel 

 to each other in the passage. At the same time other 

 muscles act on the thyroid and cricoid cartilages to separate 

 them at the top and give the cords the necessary tension. 

 With the glottis now almost closed, blasts of air from the 

 lungs strike the sharp edges of the cords and set them in 

 vibration (Fig. 150). The vocal cords do not vibrate as 

 strings, like the strings of a violin, but somewhat as reeds, 

 similar to the reeds of a French harp or reed organ. 



The location of the vocal cords in the air passages enables 

 the lungs and the muscles of respiration to aid in the pro- 

 duction of the voice. It is their function to supply the 

 necessary force for setting the cords in vibration. The 

 upper air passages (mouth, nostrils, and pharynx) supply 

 resonance chambers for reenforcing the vibrations from 

 the vocal cords, thereby greatly increasing their intensity. 

 In ordinary breathing the vocal cords are in a relaxed con- 

 dition against the sides of the larynx and are not acted 

 upon by the air as it enters or leaves the lungs. 



Pitch and Intensity of the Voice. Changes in the pitch 

 of the voice are caused mainly by variations in the tension 

 of the cords, due to the movements of the thyroid and 

 cricoid cartilages upon each other. 1 In the production of 

 tones of very high pitch, the vibrating portions of the cords 



1 Some idea of how the movements of the cartilages change the tension of the 

 cords may be obtained by holding the fingers on the larynx, between the thyroid 

 and cricoid cartilages, and making tones first of low and then of high pitch. For 



