PROBLEMATICAL ORGANS OF SENSE. 



107 



tional color. At any rate, as few of tlie colors in nature are pure, 

 but almost all arise from the combination of rays of different 

 wave-lengths, and as in such cases the visible resultant would be 

 composed not only of the rays we see, but of these and the ultra- 

 violet, it would appear that the colors of objects and the general 

 aspect of nature must j3resent to animals a very different appear- 

 ance from what it does to us. 



These considerations can not but raise the reflection how dif- 

 ferent the world may — I was going to say must — appear to other 

 animals from what it does to us. Sound is the sensation produced 

 on us when the vibrations of the air strike on the drum of our ear. 

 When they are few, the sound is deep ; as they increase in num- 

 ber, it becomes shriller and shriller ; but when they reach forty 

 thousand in a second they cease to be audible. Light is the effect 

 produced on us when waves of light strike on the eye. When four 

 hundred millions of millions of vibrations of ether strike the retina 

 in a second, they produce red, and as the number increases the 

 color passes into orange, then yellow, green, blue, and violet. But 

 between forty thousand vibrations in a second and four hundred 

 millions of millions we have no organ of sense capable of receiv- 

 ing the impression. Yet between these limits any number of sen- 

 sations may exist. We have five senses, and sometimes fancy that 

 no others are possible. But it is obvious that we can not measure 

 the infinite by our own narrow limitations. 



Moreover, looking at the question from the other side, we find 

 in animals complex organs of sense, richly supplied with nerves, 

 but the function of which we are as yet powerless to explain. 

 There may be fifty other senses as different from ours as sound 

 is from sight ; and even within the boundaries of our own senses 

 there may be endless sounds which we can not hear, and colors, 

 as different as red from green, of which we have no conception. 

 These and a thousand other questions remain for solution. The 

 familiar world which surrounds us may be a totally different 

 place to other animals. To them it may be full of music which 

 we can not hear, of color which we can not see, of sensations which 

 we can not conceive. To place stuffed birds and beasts in glass 

 cages, to arrange insects in cabinets, and dried plants in drawers, 

 is merely the drudgery and preliminary of study ; to watch their 

 habits, to understand their relations to one another, to study their 

 instincts and intelligence, to ascertain their adaptations and their 

 relations to the forces of nature, to realize what the world ap- 

 pears to them — these constitute, as it seems to me at least, the 

 true interest of natural history, and may even give us the clew 

 to senses and perceptions of which at present we have no con- 

 ception. 



