xv SPECIAL USES OF MUSCLES 215 



mouth. You can recognize a friend by his voice when 

 you do not see him. The same keys on the violin, 

 piano, and organ do not sound alike. Just so no two 

 human voices are alike, even when pitched precisely 

 to the same key. This individual peculiarity we call 

 quality or timbre. 



The lips, teeth, tongue, nose, and palate are used in 

 modifying the sounds as they come from the vocal 

 cords, and are able to change them in a wonderful way. 

 If you pinch your nose so that no air can escape 

 through it and then talk, you will see what an important 

 part the nasal passages play in ordinary conversation. 

 The loss of a single tooth is noticed in a person's 

 speech. These organs change the size and shape of 

 the various cavities through which the sound passes in 

 speaking, and so control the mode of forcing the breath 

 out. By such modifications the voivel sounds are made 

 from the pure Italian a as in arm. The subvocals are 

 made in a similar way, with the air passages more ob- 

 structed, as in the sounds r, v, m, n, etc. The aspirates 

 are mere emissions of breath more or less modified by 

 the same organs. 



Speech is simply a proper combination of sounds to 

 form words that stand for ideas. A child at birth has 

 a voice, can produce sounds as in crying and screaming, 

 but cannot speak. Language is acquired by a very 

 slow process of imitation in which the child learns to 

 control the muscles involved in producing the various 

 sounds. He must also learn the meaning of the words 

 used by others. 



