IN MEDICAL SCIENCE. 61 



appears to me to be a crucial one, proving the cor- 

 rectness of my explanation, aiid I am not aware tliat it 

 has been before instituted. 



Another point of great interest connected with the 

 physiology of vision, and involved for a long time in 

 great obscurity, is that of the adjustment of the eye to 

 different distances. Dr. Clay Wallace, of New York, 

 who published a very ingenious Httle book on the eye 

 about twenty years ago, with vignettes reminding one 

 of Bewick, was among the first, if not the first, to de- 

 scribe the ciliary muscle^ to which the power of adjust- 

 ment is generally ascribed. It is ascertained, by exact 

 experiment with the phcenidoscope, that accommodation 

 depends on change of form of the crystalline lens. 

 Where the crystalline is wanting, as Mr. Ware long 

 ago taught, no power of accommodation remains. The 

 ciliary muscle is generally thought to effect the change 

 of form of the crystalline. The power of accommoda- 

 tion is lost after the application of atropine, in conse- 

 quence, as is supposed, of the paralysis of this muscle. 

 This, I believe, is the nearest approach to a demon- 

 stration we have on this point. 



I have only time briefly to refer to Professor Draper's 

 most ingenious theory as to the photographic nature of 

 vision, for an account of which I must refer to his 

 original and interesting Treatise on Physiology. 



It were to be wished that the elaborate and very 

 interesting researches of the Marquis Corti, which have 

 revealed such singular complexity of structure in the 



