Not Always Believe Our Own Eyes and Ears 



Another trick played on the 

 eye is shown in the illustra- 

 tion at the left. A man looks 

 through a lens at an object 

 placed a short distance from 

 it. The object is then moved 

 farther away and the lens is 

 removed. The brain realizes 

 that the distance has been 

 increased and here again 

 the iris of the eye widens, 

 even though the intensity 

 of light was not altered 



Acuteness of hearing is determined by varying the 

 volume of sound let into the ear through an opening 

 in a tube. For some people the full volume of sound 

 may be audible through a tiny section of the opening 

 while others get it only through the fully opened tube 



13 



Your sensitiveness to tempera- 

 ture may be tested by placing 

 your hands in two jars of water 

 of different temperature. If the 

 hands are crossed as in the 

 picture above, it will be almost 

 impossible to tell by the sense 

 of feeling which hand is in the 

 hot water and which in cold 



Photos by Jacques Boyer 



