[ ^39 ] 



the praflice. What are the confequences of this rule ? That the 

 iris muft infallibly be wounded ; and this accounts for the com- 

 plaints ON ALL SIDES, that a part, fometimes the whole, of the 

 vitreous humour is difcharged with the cryftalline. Examine 

 the projedion of the iris and cryftalline in the annexed plates, and 

 you muft fubfcribe to this melancholy truth : But that no doubt 

 fhould remain, let it be remembered that if the iris be not 

 wounded no particle of the vitreous hutnour can efcape by mode- 

 rately preffing on the globe, after opening the cornea. We have 

 already noted that the anterior part of this humour is covered by 

 a ftrong membrane, firmly adhering to the proceflus ciliares, ex- 

 cept where it forms a fheath for the cryftalline ; what then can 

 pafs through the pupilla by preffure but this cryftalline ? The 

 vitreous membrane, and the adhefion of the iris to it, oppofe any 

 other, except the preffure be too ftrong ; but even in this cafe 

 the cataraB muji pafs through Jirji. If then a part of the vitreous 

 humour efcape, and a diftorted iris follow, we muft attribute 

 both to an abfolute mifconception of the ftrudure of the parts, 

 and to erroneous rules, the confequence of it. Thus we fee, 

 befides the unavoidable cicatrice of the cornea, other and more 

 alarming dangers are to be feared, even to the total lofs of fight, 

 notwithftanding the catarad is removed. 



But may not the ftrudure of the parts fumifii fome hints to 

 render this operation more fafe and certain ? From a careful peru- 

 fal of the foregoing very accurate defcription oif them, I think it 

 will ; and the following is the modus I would recommend. My 

 knife is of the fame fize and figure of thofe ufed in this opera- 

 tion, 



