CHAP. IIT.] SIGHT. 853 



of the three surfaces, Fig. 144 B, C. When the anterior surface of 

 the lens becomes more convex the two images reflected from that 

 surface approach each other, C, when it becomes less convex they 

 retire from each other, B. 



These observations leave no doubt that the essential change 

 by Which accommodation is effected, is an alteration of the con- 

 vexity of the anterior surface of the lens. And that the lens is 

 the agent of accommodation, is further shewn by the fact that 

 .after removal of the lens, as in the operation for cataract, the 

 power of accommodation is lost. In the cases which have been 

 recorded, where eyes from which the lens had been removed 

 seemed still to possess some accommodation, we must suppose 

 that no real accommodation took place, but that the pupil con- 

 tracted when a near object was looked at, and so assisted in 

 making vision more distinct. 



