HYGIENE OP THE EAl 23$ 



which the inner end of the stapes, or stirrup-Done, fits. 

 Behind, the vestibule opens into three semicircular canals, 

 one of which is shown at B, and in front into a spirally 

 coiled tube, S, the cochlea. 



When shakings or vibrations of the air make the tym- 

 panic membrane vibrate, it shakes the tympanic bones; 

 the stapes, vibrating in the oval foramen, then shakes 

 the liquids in the labyrinth, and sets up vibrations in 

 them, which excite the endings of the auditory nerve. 

 The stimulated auditory nerve then conveys a nervous 

 impulse to the part of the brain concerned with hearing 

 and excites it, and a sensation of sound results. 



16. Hygiene of the Ear. The outer parts of the ear 

 are less tender than the eye, and are more often injured 

 by unnecessary meddling. When the ear is healthy, its 

 wax dries up into scales and is shed in proper quantity. 

 Some of it is necessary to protect the inner parts of the 

 ear. Rubbing it out by stiff objects, not only removes 

 it too fast, but may cause inflammation of the tympanic 

 membrane. If the wax is clearly excessive, or if there is 

 any running from the ear, it is wisest to consult a physi- 

 cian at once. No stiff rod should ever be put into the 

 ear, except by a skilled person. The tympanic mem- 

 brane is very thin and may easily be torn. Young chil- 

 dren often put such things as peas and small beans in 

 their ears. If they do not come out very easily, get a 

 doctor to rejnove them. In any such case, do not pour 



the semicircular canals ? The cochlea ? Describe how the endings of 

 the auditory nerve are excited by vibrations of the air. What results 

 when the auditory nerve is stimulated ? 



16. Why are the ears more often injured than the eyes by meddling ? 

 What happens to the wax of the ear in health ? Why is some wax 

 necessary ? What may result from removing it ? What should be 

 done when there is any running from the ear? When a child has put 



