V. ON THE 



MECHANISM OF THE EYE. 



BY 



/ 



THOMAS YOUNG, M.D. F.R.S. 



FROM THE PHILOSOPHICAL TRANSACTIONS. 



Read before the Royal Society, November 27, 1800. 



I. XN the year 1793, I had the honour of 

 laying before the Royal Society some ob- 

 servations, on the faculty, by which the eye 

 accommodates itself to the perception of ob- 

 jects at different distances*. The opinion 

 which 1 then entertained, although it had 

 never been placed exactly in the same light, 

 was neither so new, nor so much forgotten, 

 as was supposed by myself, and by most of 

 those with whom I had any intercourse on 

 the subject. Mr. Hunter, who had long 

 before formed a similar opinion, was still less 

 aware of having been anticipated in it, and 

 was engaged, at the time of his death, in an 

 investigation of the facts relative to it "I- ; an 

 investigation for which, as far as physiology 

 was concerned, he was undoubtedly well 

 qualified. Mr. Home, with the assistance 



• Phil. Trans. 1793.169. 

 t Phil. Trans. 1794. 21. 

 jPhil. Trans. 1795. 1. 



of Mr. Ramsden, whose recent loss this So- 

 ciety cannot but lament, continued the 

 inquiry which Mr. Hunter had begun ; and 

 the results of his experiments appeared very 

 satisfactorily to confute the hypothesis of the 

 muscularity of the crystalline lens J. I there- 

 fore thought it incumbent on me, to take the 

 earliest opportunity of testifying my persua- 

 sion of the justice of Mr. Home's conclusions, 

 which I accordingly mentioned in a Disser- 

 tation published at Gottingen in 1796 §, and 

 also in an Essay presented last year to this 

 Society ||. About three months ago, I was 

 induced to resume the subject, by perusing 

 Dr. Porterfield's paper on the internal mo- 

 tions of the eye ^ ; and I have very unex- 

 pectedly made some observations, which, I 

 think I may venture to say, appear to be 



§ De Corporis humani Viribus conservatricibus, p. (58. 



II Phil. Trans. 1800. 148. 



f Edinb. Med. Essays. IV. 13*. 



