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clofely is this attached to thefe radiated fibres that their im- 

 preffions are funk deep into it, and may be called the fulci of 

 the proceffus ciliares. This firft range of fibres on the infide of 

 the iris is in a human eye aboQt the breadth of a line; a kind of 

 tendinous narrow and circular band clofes this phalanx, and from 

 thence proceeds a fecond row of radiated fibres thinner than the 

 firft ; thefe alfo adhere and leave their imprefllons on the vitreous 

 membrane ; and that part of the iris which forms the pupilla 

 is ftill finer than the laft-mentioned, refts on the cryftalHne, and 

 is quite free from any adherence, by which means it contradls 

 or dilates in proportion to the vicinity or diftance of objeds. 

 Thus the convexity of the iris follows nearly that of the cornea 

 tranfparens, and is occafioned by the protuberance of the cryftal- 

 linc ; fo that the idea of a pofterior chamber of the aqueous 

 humour muft be for ever banished ; nor is that of circular 

 fibres belonging to the iris better founded in truth and anatomy. 

 Thefe laft wc are conftantly told were formed for the purpofe of 

 contradting, as the radial ones were for expanding, the pupilla; 

 hut not to advert to a fad, which is, that the ftate of q\]iefcence 

 in the pupilla is its dilatibility, which is evident, becaufe when 

 afleep or in a ftate of imttention with refped to objefls, we 

 conftantly find it fi ; I fhall juft obferve that there are none 

 but radial fibres throusih the whole internal furface of the iris. 

 That the convexity of the iris may be proved beyond a pbffibility 

 of doubt, let the fide of the cornea be pierced at its jundion 

 with the fclerotica by a lancet or catarad needle, and paffcd in 

 that ditedion to the oppofiie fide of the eye. On examination 

 you will find, that beliJes the cornea you will have wounded the 



iris 



