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A TEXTBOOK OF PHYSIOLOGY 



the cords vibrate in their whole length, the pressure of the air is re- 

 latively large, the volume of air used small, and the strain of production 

 not great. In using the head register, the chink is wider and shorter, 

 the hind part closed, the pressure of the air smaller, but more air is 

 used, and so the strain is greater. 



The internal fibres of the thyro-arytenoids may contract alone, so 

 that the inner edges of the cords are rendered tense, while the outer 

 thicker parts are slack. In whispering the air rustles past the opened 

 cords. 



While the pitch of the voice is given by the number of vibrations 

 of the cords per second, the changing quality depends on the resona- 

 tion of certain of the overtones in the resonating cavities formed by 

 mouth, nose, and throat. The mouth can be shut up almost by 



Position of rest. (The vocal cords are 4 Position during forced inspiration. (The 

 midway btt.veen abduction and ad- j ' vocal cords are in extreme abduc- 

 duction ) ir, ' 



Position during vocalization. (" Chest 

 voice.") The vocal cords are ad- 

 ducted and vibrating in their entire 

 length. 



Position during vocalization. (Cahetto 

 voice.) The vocal cords are adducted 

 and vibrating in their anteiior por- 

 tions onlv. 



FlO. 4!)5 TlAGRAMS TO ILLUSTRATE THE POSITION OF THE 'VOCAL CORDS UNDER 

 VARIOUS CIRCUMSTANCES. 



raising up the tongue and drawing in the cheeks, or it can be opened 

 so as to form a wide cavity. The pillars of the fauces are flexible, 

 and can be brought forwards against the tongue, or pulled widely 

 apart. The soft palate, by sinking, can throw the nose into the resonat- 

 ing cavity and cut off the mouth, or, by rising, cut off the nose. By a 

 mean position both cavities may come into play. The tongue can 

 widen or narrow the mouth cavity, divide it into sections and connect 

 these by slits, or cut them off from one another. In the chest register 

 the passage for the voice is wide and the chest cavity amplifies the 

 resonance. In the head register the passage is narrow and the reson- 

 ance is confined to the cavities of the head. While in singing and 

 vocalization the vocal cords twang, in whispered speech the resonating 

 cavities alone suffice for the production of speech. 



