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ments, and for the time the moft difficult to be anfwered, was 

 this — " It is an acknowledged fad that the cryftalline is placed in 

 " the centre of the eye ; but every oculifl knows that the opaque 

 " body to be removed lies immediately behind the pupilla, there- 

 " fore it muft be a membrane between the cryflalline and iris." 

 This put the advocates for the new dodtrine on a clofer exa- 

 mination of the ftrudure of the eye, in which Briffeau, Maitre 

 Jean and St. Yves, but more particularly Heifter, Morgagni, 

 Petel and Winflow, bore diftinguifhed parts. Every new enquiry 

 contributed to advance the feat of the cryftalline more forward, 

 'till at length, in the year 1729, Doftor Petel [publifhed a letter* 

 in anfwcr to fome remarks of Hequet's, in which he demonftrated 

 that the cryftalline was fo near the pupilla that it was impojjlble to 

 introduce a cataraSl needle between it and the iris without wounding it ! 

 And to make clear to every conception this fad, he gave with 

 this letter a figure of the eye, more corred that any that had yet 

 appeared. Still he kept up the diftindion of the different cham- 

 bers of the eye, and in this figure determined their limits, which 

 have been carefully noted by all fubfequent writers. But that 

 moderns fhould appear no more defedive in point of theory and 

 optics than the ancients, the limited fight that followed the 

 operation was accounted for by obferving, " that the cryftalline is 

 " a denfer medium than either the aqueous or vitreous humour, 

 " and of courfe by its removal fight fhould be proportionably 

 *' weaker." 



Sur la vrai fituation du Criflalin. 



R 2 Anaioynical 



