398 THE SENSORIAL FUNCTIONS. 



Chapter VI. 



VISION. 



§ 1 . Object of the Sense of Vision. 



To those who study nature with a view to the dis- 

 covery of final causes, no subject can be more in- 

 teresting or instructive than the physiology of 

 Vision, the most refined and most admirable of all 

 our senses. However well we may be acquainted 

 with the construction of any particular part of the 

 animal frame, it is evident that we can never form 

 a correct estimate of the excellence of its mecha- 

 nism, unless we have also a knowledge of the pur- 

 poses to be answered by it, and of the means by 

 which those purposes can be accomplished. Innu- 

 merable are the works of creation, the art and con- 

 trivance of which we are incompetent to under- 

 stand, because we perceive only the ultimate 

 effects, and remain ignorant of the operations by 

 which those effects are produced. In attempting 

 to investigate these obscure functions of the animal 

 or vegetable economy, we might fancy ourselves 

 engaged in the perusal of a volume, written in some 

 unknown language, where we have penetrated the 

 meaning of a few words and sentences, sufficient 

 to show us that the whole is pregnant with the 

 deepest thought, and conveys a tale of surpassing 

 interest and wonder, but where we are left to gather 

 the sense of connecting passages by the guidance 



