The Senses and the 'Nervous System 77 



of the laws of refraction, become slightly less. He will, there- 

 fore, occupy a slightly smaller portion of the window, and 

 will appear to the fish to grow smaller. 



And so we see that as the fish rises in the water objects 

 may appear to shrink or expand or remain the same size, 

 depending upon their location. To us, accustomed to having 

 all things grow larger as we approach them, smaller as we 

 \^ithdraw from them, it seems as if the fish must have a 

 pretty cock-eyed idea of what the world is likej but as he is 

 used to it, it doubtless seems perfectly normal to him. Which 

 leads us to speculate as to what distortions there may be in 

 our own view of the universe, and how far it is from being 

 the "normal" which it appears to our eyes. 



Theoretically the whole world above water, right out to 

 the horizon, is visible to the fish as a border on the inner 

 edge of his window, but under natural conditions this is not 



r 



Diagram J 



entirely true. In the laboratory, an eye just above the sur- 

 face at E clearly sees the object F, at a new position F', if 

 there is a screen SS to cut off any light which might other- 

 wise be coming from the direction L (Diagram J). You can 

 demonstrate this by sinking the cap of a toothpaste tube at 

 one end of the bathtub and placing your eye at the surface at 

 the other end, with the light behind you. On the other hand, 

 if light is coming from the direction L, so much of it is 



