THE CILIARY BODY AND LENS 



825 



will be found that on near vision the corneal image (a) retains its po- 

 sition, size and form, while the one reflected from the anterior surface 

 of the lens (b), becomes smaller in size and more rounded, and moves 

 toward the corneal image. A very slight diminution in size is also 

 displayed by the image reflected from the posterior surface of the lens 



FIG. 431. REFLECTED IMAGES OF A CANDLE FLAME AS SEEN IN THE PUPIL OF AN EYE AT 

 REST AND ACCOMMODATED FOR NEAR OBJECTS. (Williams.) 



(c). It need scarcely be mentioned that these changes are associated 

 with a constriction of the pupil (Descartes, 1637), and that all the 

 aforesaid alterations are reversed on far vision. Since near vision is 

 an active muscular process, it is accomplished less speedily than the 

 accommodation for far objects. 



FIG. 432. DIAGRAM EXPLAINING THE CHANGE IN THE POSITION OF THE IMAGE REFLECTED 

 FROM THE ANTERIOR SURFACE OF THE CRYSTALLINE LENS. (Williams, after Bonders.) 



The lesson to be derived from this experiment is that the curvature 

 of the cornea remains absolutely the same, while that of the posterior 

 surface of the lens suffers only the slightest possible alteration. By 

 far the greatest change takes place at the anterior surface of the lens, 

 which, on near vision, becomes more convex and therefore forces the 



