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ELEMENTARY PHYSIOLOGY 



16. Speech.— Speech is voice modulated by the throat, 

 tongue, and lips. Thus, voice may exist without speech ; 

 and it is commonly said that speech may exist without 

 voice, as in whispering. This is only true, however, if 

 the title of voice be restricted to the sound produced by 

 the vibration of the vocal cords ; for, in whispering, there 

 is a sort of voice produced by the vibration of the 

 muscular walls of the lips which thus replace the vocal 

 cords. A whisper is, in fact, a very low wliistle. 



Fio. 107. 

 Diagram of a model illustrating the action of the levers and muscles of 

 the larynx. The stand and vertical pillar represent the cricoid and 

 arytenoid cartilages, while the rod (be), moving on a pivot at c, takes the 

 place of the thyroid cai-tilage ; d 6 is an elastic l)and representing the 

 vocal ligament. Parallel witli this runs a cord fastened at one end to the 

 rod 6 c, and, at the other, passing over a pulley to the weight B. This 

 represents the thyro-arytenoid muscle. A cord attached to the middle of 

 6 c, anti passing over a second pulley to the weight A, represents the 

 crico-thyroid muscle. It is obvious that when the bar (b c) is pulled down 

 to the position c d, the elastic band (a 6) is put on the srtretch. 



The modulation of the voice into speech is effected by 

 changing the form of the cavity of the mouth and nose, 

 by the action of the muscles which move the walls of 

 those parts. 



Thus, if the pure vowel sounds — 



E (as in he), A (as in hay). A' (as in ah), 



(as in or), 0' (;is in oh), 00 (as in cool), 



are pronounced successively, it will be found that they 



