372 THE SENSORIAL FUNCTIONS. 



movements which originally, and of themselves, 

 appear, in most animals, to be productive of 

 great enjoyment. 



To a person unused to reflection, the pheno- 

 mena of sensation and perception may appear to 

 require no elaborate investigation. That he 

 may behold external objects, nothing more seems 

 necessary than directing his eyes towards them. 

 He feels as if the sight of those objects were a 

 necessary consequence of the motion of his eye- 

 balls, and he dreams not that there can be any 

 thing marvellous in the function of the eye, or 

 that any other organ is concerned in this simple 

 act of vision. If he wishes to ascertain the 

 solidity of an object within his reach, he knows 

 that he has but to stretch forth his hand, and to 

 feel in what degree it resists the pressure he 

 gives to it. No exertion even of this kind is 

 required for hearing the voices of his companions, 

 or being apprized, by the increasing loudness of 

 the sound of falling waters, as he advances in a 

 particular direction, that he is coming nearer 

 and nearer to the cataract. Yet how much is 

 really implied in all these apparently simple 

 phenomena ! Science has taught us that these 

 perceptions of external objects, far from being 

 direct or intuitive, are only the final results of a 

 long series of operations, produced by agents of 

 a most subtle nature, which act by curious and 

 complicated laws, upon a refined organization, 



