THE EAR 301 



cords are naturally much longer and coarser. The difference 

 between a soprano and an alto voice is merely one of length 

 and tension of the vocal cords. 



Successful singing is possible only when the vocal cords 

 are readily flexible and when the singer can supply a steady, 

 continuous blast of air through the slit between the cords. 

 The hoarseness which frequently accompanies cold in the 

 head is due to the filling up of the slit with mucus, because 

 when this happens, the vocal cords cannot vibrate properly. 



The sounds produced by the vocal cords are transformed 

 into speech by the help of the tongue and lips which modify 

 the shape of the mouth cavity. How this is accomplished is 

 unknown ; many animals have a speaking apparatus similar 

 to our own, nevertheless man is the only animal able to 

 transform sound into speech. The birds use their vocal 

 cords to beautiful advantage in singing, far surpassing us in 

 many ways, but the power of speech is lacking. 



276. The Ear. The pulses created in the air by a sound- 

 ing body are received by the ear and transmitted by the 

 auditory nerve to the brain, where they produce the sensation 

 of sound. The ear is capable of marvelous discrimination 

 and accuracy. " In order to form an idea of the extent of 

 this power imagine an auditor in a large music hall where a 

 full band and chorus are performing. Here, there are 

 sounds mingled together of all varieties of pitch, loudness, 

 and quality ; stringed instruments, wood instruments, brass 

 instruments, and voices of many different kinds. And in 

 addition to these there may be all sorts of accidental and 

 irregular sounds and noises, such as the trampling and shuf- 

 fling of feet, the hum of voices, the rustle of dress, the creak- 

 ing of doors, and many others. Now it must be remembered 

 that the only means the ear has of becoming aware of these 

 simultaneous sounds is by the condensations and rarefac- 



