THE SENSES 147 



In a carriage or a railway car, your paper will shake, 

 and you must be continually moving your eyes to see. This 

 makes the eyes ache. You ought not to try to read under 

 these conditions. 



When you read while lying down, you turn your eyes 

 in the direction of your feet, which is very tiresome. 



290. Nearsightedness. In order to see objects clearly, 

 some persons must hold them close to their eyes. This 

 is called nearsightedness. Nearsighted persons should 

 always wear spectacles. This will enable them to see as 

 well as any one. 



291. Farsightedness. As persons grow old, they can- 

 not see near by so well as afar off. This is called far- 

 sightedness. By wearing spectacles, they can see as well 

 as ever. 



292. Alcohol and the eyes. Alcohol causes the eyes 

 to look red, and may make them sore. In some cases 

 it causes the nerves of the eye to waste away. Then the 

 eye will be blind, although it will appear well. 



In drunken persons the muscles of the eyes, like the 

 muscles of the legs, do not act rightly. They often turn 

 the eyes in different directions. Then the person will be 

 cross-eyed, and every object will seem double. 



Tobacco, in some cases, causes the nerve of sight to waste 

 away. Tobacco smoke makes the eyes smart so that the 

 tears flow. 



293. The ears. We hear with our ears. Sound is 

 made by waves of air which beat upon special nerves. 

 The ear is a cavity, hollowed out of a very hard bone, 

 and is divided into three parts. 



294. The outer ear. The outer ear, which we see, is 

 not needed, but it does some good in catching the waves 

 of sound and throwing them into the tube in its center. 



