1158 ACCOMMODATION. [BOOK HI. 



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 accommo- 

 dation 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 contracted when a near object was 

 looked at, and so assisted in making vision more distinct. 



To understand, however, the mechanism by which this change 

 in the anterior surface of the lens is brought about, we must turn 

 to some further details of the structure of the eye. 



