PART IV. 



PHYSIOLOGICAL PARADOXES. 

 I. 



THE EYES, AND PECULIARITIES OF VISION. 

 i. A Blind Spot in a Sound Eye. 



'CLOSE the left eye by putting the left hand 

 over it if necessary and then holding Fig. 45 

 level, look with the right eye at the letter R. 

 Although you are looking at R directly, you 

 can quite easily see L at the side, without 

 changing the direction of your glance. We 

 can see many things " out of the tail of our 

 eye " while directing the gaze at something 

 else. If the sheet with the letters on it is 

 about ten inches off, bring it slowly nearer, 

 still keeping the two letters level. At about six 

 inches distance from the eye the letter L dis- 

 appears from view. A moment before you 

 were not looking at it, but you saw it at the 

 side. Now you are not looking at it, and you 

 do not see it, unless you take your gaze off R. 

 But keep your gaze on R as before, and bring 

 the paper still nearer, keeping it level. L 

 comes into view again. 



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