386 CIRCULATION AND RESPIRATION 



the larynx, and bring the edges of the cords near each 

 other. The air that passes through the larynx makes the 

 cords vibrate, producing sounds. The sounds are soft or 

 loud according to the amount of air used. 



The pitch of the voice (cf. 192) depends chiefly upon 

 the degree of tightness of the vocal cords, and upon their 

 length. When the cords are tightly drawn, and short, 

 they vibrate more rapidly than when loose and long; 

 hence they produce sounds of higher pitch. A man has 

 a larger larynx than a woman has, and his vocal cords are 

 larger and longer. As a result his voice is of lower pitch. 



390. Speech. We use the vocal cords in ordinary speaking and 

 singing, yet we can "whisper" words without using the vocal cords 

 at all. We make the whispered words with the throat, tongue, teeth, 

 and lips. When we want to give loudness and pitch to our words, we 

 force the necessary amount of air over the vocal cords. The throat, 

 mouth, and nostrils also strengthen the sounds that come from the 

 vocal cords. The quality of a voice is that peculiarity which distin- 

 guishes one voice from another. By means of it we recognize the 

 voices of our friends. Voice quality depends on the special shape of 

 the air passages and mouth in each person, and on the peculiar way in 

 which each of us uses them in speaking and singing. 



Vowels, or "vocals" (a, e, i, o, u, and y) are the vocal-cord sounds 

 that are changed least by the mouth, tongue, lips, etc.; consonants are 

 greatly altered forms of these sounds. 



391. Care of the Organs of Respiration. In our 

 breathing, as in eating and drinking, we are taking ex- 

 ternal material into the body. If there are disease germs 

 in this material, they have opportunity to develop and to 

 cause disease. We therefore need to guard against 

 throat and lung diseases, as well as against typhoid. The 



