336 THE HUMAN BODY. 



While every one's voice has a certain natural pitch which 

 leads us to call it soprano, tenor, bass, and so forth, this 

 pitch can be modified within limits, so that we each can 

 sing a number of notes. This variety is due to the action 

 of muscles in the larynx which alter the tension of the 

 vocal cords; the more tightly these are stretched, other 

 things being equal, the higher pitched is the tone which 

 they emit. 



Speech. The vocal cords alone would produce but feeble 

 sounds. If a fiddle-string be attached to a hook on the 

 ceiling and stretched by hanging a heavy weight on its 

 lower end, we can get tones out of it when it is plucked 

 or bowed; but the tones are feeble and deficient in charac- 

 ter and fullness. In the violin the strings are attached to a 

 hollow wooden box, and when the string is set in move- 

 ment it causes the wood to vibrate, and this, in turn, the air 

 contained in the cavity of the instrument; in this way the 

 tone is intensified, and altered and much improved in 

 quality. The air in the pharynx, mouth, and nose an- 

 swers pretty much to that in the hollow of the violin; those 

 cavities together form a resonance-chamber, and when the 

 vocal cords vibrate they set this air in vibration also, and 

 so the sound is made louder and is altered in character. 

 By movements of throat, soft palate, tongue, cheeks, and 

 lips, the size and form of the sounding'chamber are varied, 

 and with them the tone of voice; by movements of tongue, 

 lips, and palate, the air-current, and therefore the sound, 

 is interrupted from time to time; on other occasions the 



How is it that we can sing a number of notes of different pitch? 



Why is a hollow wooden box an essential part of a violin? How 

 do the throat and mouth cavities influence the loudness and quality 

 of the voice? How do tongue, lips, and cheeks co-operate in con- 

 verting voice into speech? 



