1 62 THE HUMAN BODY. 



rabbits, for example, which are destitute of pigment, and in 

 which the sclerotic and choroid are transparent, we may see, 

 as Magendie pointed out, the flame of a candle reversed upon 

 the retina. 



How then are we able to see objects in their real position? 

 BufTon and others have asserted that reason enables us to 

 restore the image depicted on the retina to its real position, 

 that touch enables us to rectify the visual sensation. But 

 Cheselden, having by an operation enabled a patient born 

 blind to see, does not state that the young man first saw 

 objects otherwise than in their real position; and the careful 

 observations made by this skilful surgeon do not permit us 



Fig. 37. Course of the luminous rays in the eye. 



H, M, P. Luminous rays emanating from an object, 

 h, m, p. Lviminous rays refracted, forming the inverted 

 image on the retina. 



to suppose that a circumstance of such importance could 

 escape his notice. According to M. Lame, we know that 

 objects are upright although we see them inverted, from the 

 consciousness of the movements which we give to the optical 

 axes of our eyes in looking successively at the different 

 points of objects from top to bottom. 



Miiller avers that we see the objects inverted, but that all 

 presenting themselves to us under the same relative condi- 

 tions of position, nothing can appear inverted because we 

 see everything in the same position, and that our notions of 

 uprightness or inversion only exist by opposition. 



