PERCEPTIONS OF ANIMALS. -513 



conceive how the limits of visible colour may be 

 established ; for if there be no nervous fibres in 

 unison with vibrations more or less frequent than 

 certain limits, such vibrations, though they reach 

 the retina, will produce no sensation. Thus it is 

 perfectly possible that insects, and other animals, 

 may be incapable of being aftected by any of the 

 colours which we perceive ; while they may be 

 susceptible of receiving distinct luminous impres- 

 sions from a class of vibrations which, applied to 

 our visual organs, excite no sensation.* The func- 

 tions of the antennpe, which, though of various 

 forms, are organs universally met with in this class 

 of animals, must be of great importance, though 

 obscurely known ; for insects when deprived of 

 them appear to be quite lost and bewildered. 



The Torpedo, the Gymnotus, and several other 

 fishes, are furnished with an electrical apparatus, 

 resembling the Voltaic battery, which they have 

 the power of charging and discharging at pleasure. 

 An immense profusion of nerves is distributed upon 

 this organ ; and we can hardly doubt that they 

 communicate perceptions, with regard to electri- 

 city, very different from any that we can feel. In 

 general, indeed, it may be remarked, that the more 

 an organ of sense diifers in its structure from those 

 which we ourselves possess, the more uncertain 

 must be our knowledge of its functions. We may, 

 without any great stretch of fancy, conceive our- 

 selves placed in the situation of the beasts of the 

 forest, and comprehend what are the feelings and 

 motives which animate the quadruped and the 



* Encyclopaedia Metropolitana, Article " Light." 

 VOL. II. L L 



