PHYSIOLOGY OF VISION. 167 



the eye the cause of this imperfection is avoided, and this, 

 too, without the least inconvenience to ourselves. Since 

 no one in health, has ever yet complained of the slightest 

 difficulty in making the highest parts of objects appear 

 at the greatest distance from the surface of the earth, 

 whether he knew that he saw them in another position 

 or not. 



505. Now we have every reason to believe that our 

 Creator, all things considered, has constructed us on the 

 wisest and best plan, and therefore, that he chose so to 

 endow us, whether by a peculiar faculty or not, as to see 

 things as they exist, though they are inverted in the eye, 

 rather than to correct this inversion by an additional lens. 

 This seems to be the only explanation which it is neces- 

 sary to give this subject, for although physiologists have 

 puzzled themselves to show how it is that we see objects 

 as we do, when ail agree that the structure of the eye in- 

 verts them ; still, we can discern no more difficulty in this 

 phenomenon than we do in the fact that an engraver re- 

 verses all his lines, and that a printer reads his type w r ith 

 the same facility that he does a printed page ; both being 

 matters of habit and experience. 



506. Minuteness of the Image on the Retina. It would 

 be a curious and not uninstructive subject, as displaying 

 in a very striking manner, the wisdom and power of God, 

 in the mechanism of his creatures, to estimate the dimen- 

 sions of the images of different objects at various distan- 

 ces on the retina, if indeed this could be done with any 

 accuracy. 



507. The expansion of the optic nerve which forms 

 the seat of vision, is only about half an inch in diameter, 

 and yet, on this space is painted with the most perfect 

 accuracy, the image of every object which the eye be- 

 holds. Now the eye in an elevated situation may look on 

 the whole of a landscape, to the distance of fifty miles ; 

 and, without perceptibly moving the visual organs, include 

 a lateral view of probably twenty-five miles ; and yet the 



How might the inversion of the picture on the retina have been correct- 

 ed ? Why do we see things perpendicularly ? 



