LOOKING THROUGH THE HAND. 



objects which are visible outside the central 

 line of sight. If we look steadily at a picture 

 on the other side of the room, and two yards 

 from the picture is a person at whom we are 

 not looking, although we can see quite well 

 whether that person is reading, writing, or 

 playing cards, as a rule we neglect to note 

 such points because our interest in the picture 

 is keeping upon it the attention of our eyes. 



Secondly, we can neglect things that are 

 at the wrong distance for clear vision. We can 

 focus objects at which we wish to look, as 

 truly as a camera or a telescope can. We do it 

 by using certain muscles of the eye to alter 

 the shape of the lens. And when the lens is 

 set for a certain object, others before and be- 

 hind it are out of focus and consequently ill- 

 defined. This helps us to neglect them, and 

 so to escape living in a world of doubles. For, 

 as we saw in the last section, the convergence 

 of the eyes upon the object looked at causes 

 nearer and farther objects to appear duplicated. 



Lastly, when one eye only can see the ob- 

 ject we wish to look at, we neglect the things 

 seen at the same time by the other. A rifle- 

 man can perfectly well learn to sight the target 

 with his right eye without for a moment closing 

 the left. He can neglect its vision for the 

 time being. 



Similarly, in the foregoing experiment, the 

 left eye, looking through the tube at the 



227 



