HOW WE HEAR 



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membrane. If this membrane is broken, hearing is im- 

 paired, and therefore children should be very careful not to 

 stick a pointed instrument into the ear, and if anything gets 

 into the ear, they should not try to get it out themselves, 

 but should get help from some one who knows how to handle 

 the ear. In the middle ear are three tiny bones. These 

 serve as a bridge to carry the sound waves from the outer 

 ear into the inner ear. Waves hit against the membrane 



Parts of the ear. Notice the three little bones in the middle ear. 



and cause it to vibrate, and are transferred to the mid- 

 dle ear. Here deep in an opening in the bone of the 

 skull is an instrument a thousand times more delicate 

 than the most wonderful piano in existence. This in- 

 strument receives the sound waves and transfers them to 

 the brain. 



The ear is also a balancing organ, and in many lower 

 animals has this function only. Our equilibrium is main- 

 tained by means of three so-called semi-circular canals 

 which are set into the opening at different angles. Those 

 men who wish to become aviators must have a perfect 



