HELMHOLTZ IN KONIGSBERG 



optical constants as they exist for near and distant 

 vision in accommodation. He then found that the 

 positions of these constants, such as the position of 

 the anterior focus, the positions of the nodal and 

 principal points, and the posterior focus, varied for 

 near and far vision as they would do if the only 

 changes occurring during the mechanism were in the 

 curvatures of the anterior and posterior surfaces of 

 the lens, as ascertained by experiment and measure- 

 ment by the ophthalmometer. So the question was 

 finally settled. The discovery of the part played 

 by the lens in accommodation is one of the greatest 

 triumphs in modern physiology. Lucid mathematical 

 and experimental proofs have been given of its 

 correctness, and all other theories have been entirely 

 abandoned. 



103 



