in ON ANIMAL LIFE 87 



We are too apt to suppose that the senses 

 of animals must closely resemble, and be con- 

 fined to ours. 



No one can doubt that the sensations of 

 other animals differ in many ways from ours. 

 Their organs are sometimes constructed on 

 different principles, and situated in very un- 

 expected places. There are animals which 

 have eyes on their backs, ears in their legs, 

 and sing through their sides. 



We all know that the senses of animals are 

 in many cases much more acute than ours, as 

 for instance the power of scent in the dog, of 

 sight in the eagle. Moreover, our eye is 

 much more sensitive to some colours than to 

 others ; least so to crimson, then successively 

 to red, orange, yellow, blue, and green ; the 

 sensitiveness for green being as much as 750 

 times as great as for red. This alone may 

 make objects appear of very different colours 

 to different animals. 



Nor is the difference one of degree merely. 

 The rainbow, as we see it, consists of seven 

 colours — red, orange, yellow, green, blue, 

 indigo, and violet. But though the red and 



