406 A YEAR IN SCIENCE 



which we read should be good, but not too bright; it 

 should come from above or from one side. Care should 

 be taken to avoid having bright lights shine directly 

 into the eyes, or having it reflected into them from the 

 page. A flickering light is very tiresome. Reading in 

 the cars is extremely taxing because the eye is strained 

 in trying to follow the book which is constantly being 

 moved by the jarring of the car. The distance at 

 which a book should be held will vary somewhat, but 

 twelve to fifteen inches is the best distance for steady 

 reading. 



The eyes should not be rubbed, for they might 

 become infected by germs on the fingers. Dust is also 

 bad for the eyes. It sometimes contains harmful 

 germs, and it always irritates them. A saturated solu- 

 tion of boracic acid is best for washing inflamed eyes. 



The ear. If a bell is struck, it is made to vibrate. 

 This causes the air in all directions around the bell 

 to vibrate, and waves of sound are produced. Some of 

 these waves of sound enter the ear, are conducted through 

 the ear, and finally stimulate the ends of the auditory 

 nerve from which nerve currents are sent to the brain. 



Structure of the ear. The ear is divided into three 

 parts : the external, the middle, and the internal ear. 



1. The external ear consists of the oval, more or 

 less flattened structure at the side of the head. It is 

 composed of cartilage and skin. It collects sound 

 waves and helps to converge them into the auditory 

 canal which is the tube leading to the middle ear. 



