RESPIRATION 



8 9 



When they are tightened and brought near together, and 

 a breath of air is driven out through them, a noise is made. 

 The sound varies with the tightness and the nearness to- 

 gether of the cords, and the force with which air is driven 

 out. It is further changed by the mouth and nose, which 

 act as a sounding box. In talking, the tongue and lips are 

 moved so as to make different kinds of sounds. These 

 sounds are so very much alike that the sounds of a for- 

 eigner's language seem the same, no matter what he is 

 saying. Yet we learn to make the sounds with great ex- 

 actness and rapidity, and to tell their difference easily. 



Top view of the larynx, with the 

 vocal cords closed, as in speaking. 



a epiglottis. b vocal cords. 



Top view of the larynx, with the 

 vocal cords open, as in breathing. 



a epiglottis. b vocal cords. 



163. Care of the voice. The larynx becomes tired, like 

 any other part of the body. So it is harmful to strain the 

 voice by loud shouting or singing. Breathing through the 

 mouth is also harmful, especially if the air be cold or 

 damp. Using the voice while the throat is sore is also 

 harmful. Singing notes of very high pitch is also very 

 tiresome to the voice. 



It is easy to form the habit of talking in loud, coarse 

 tones. Now the tones of the voice express our feelings. 

 We ought to be careful always to speak in pleasant tones 

 so as to make others feel happy even if we are not happy. 

 Then we ourselves shall be more likely to be happy. 



164. Alcohol and oxidation. We have already studied 



