nv h THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES GIFT Dr. M. K. Beigelman ANEW TREATISE, j //tJ- on the l^M^Jc^ GLAUCOMA, / / / CATARACT. BY SILVESTER 6 H ALLORAN, of Limerick* Surgeon* Verdei tempttSt quo, ijla qua nufic latenty txtrahtt. in lucent dies Seneca. Uniut lahcTf nulterum lahorem alle^at. D U el/ LIN: Panted Ijv S. Powell, In Crant-hrit. M DCC I,, /"] Vs' T O Richard Mead, Efc^; Of the College of Physicians, London; Fellow of the Royal Society y &c. Learned Sir, IT is a Complaint made by the 'judicious Heifier, that few People attend to the Study of the Eye, or it's Diforders, with the At- A tention DEDICATION. tention which fo delicate a Subje6t requires ; tho' cer- tainly the moft entertaining for Speculation, and the moft ufeful with refped: to Pra6tice. But various things have concurred to difcredit this Study ; the uncertain Method of treating thofe Diforders ; the various Sen- timents of Authors, on the Seat and Nature of a Cata- rciB ; their confus'd Diffe- rences between it and the Glaucoma ; and the very few regular Surgeons, who have DEDICATION. have publickly profefTed any Knowledge of it, have all together heaped fuch a Load of Calumny on it? that it feemed dangerous for any one, mindful of his own CharaBer, to make any At- tempt, to refcue it from the many Injuries it lay under. Yet have there of late Years appeared Perfons, who, more regardful of the Honour of Medicine y than of the private Infmuations, and Slanders of fome of the ProfejSbrs of it, have dared to fhevr^ A 2 the DEDICATION. tlie true Caufes and Cures of the Diforders of this beau- tiful and moft ufeful Organ; amongft whom? we muft, with Honour, mention, a Petit, a BriJfeaUj and a Ran- But tho' thefe generous Attempts, had caufed the Difeafes of the Eye^ to be more particularly regarded, by Phyficians and Surgeons^ yet did there ftill remain Di& faculties almoft infurmount- able, to the entire clearing them DEDICATION. them up? and particularly the Catara^. This bold Task I have attempted, tho' a laborious Work-, and worthy of a better Pen ! I had the Honour of laying it before Y0U5 foon after my quitting Paris, tho' then almofl: in it's Infancy You, Sir^ were pleafed to think the At- tempt laudable, and the Per- formance not unworthy pub- lick Notice. The Counte- nance of a Gentleman, de- fervedly the Head of hisPro- feilion, and the Hippocrates of ' DEDICATION. of the prefent Age, could not but raife a ftrong Defire in me really to merit Your Efteem. Spurred on by this Principle, I have with incre- dible Labour and Perfeve- rance, purfued the Attempt ; and found, however beaten the Subjedl:, my Pains am-^ ply rewarded by the Difco- veries I have made. But tho* the Approbation of a College of Phyficians, would no Way raife the Ef^ teem of fuch a Thing in You: DEDICATION You ; as being Yourfelf a thorough Judge of Merit ; yet it would certainly make the World, look with more Deference on fuch a Perfor- mance. It was on this Ac- count? that I laid the Manu- fcripts before Dr. Barry, Pre- (ident of the College of Phy- fcianS'i for their Examina^ tioriy who had been previ- oufly acquainted of it, by Letter, from one of the Cenfors, and my honoured Friend. But tho' it remai- ned there for above a Week, and DEDICATION. and that there had been a full Affembly of that learn- ed Body, in the Interim^ be- fore whom I propofed to de- monftrate the Fa£ts herein contained ; yet I found they had neither Time, nor Curio- fty ^y to fee thofe Things ; and they declined approving of it, becaufe looking over the Authors here quoted, would take up too much Time. Thus much I thought proper to infert, in my own Defence. But it is cer- tain, * Hequefs Anfwer to Dr, Peiifz Letter. DEDICATION, taiiij that a good Performance needs not Commendation; and a bad one, ufhered in with how pompous an one foever, will not be fufficient to protect it. The Truth of the latter Part of this Af- fertion^ thofe Gentlemen can atteftj and the former needs no Proof. But tho' I had not the Pleafure of their Approba- tion? yet I doubt not, but the Attempt I have made? to ref- cue fo valuable a Branch of [B] Phyjich DEDICATION. Phyfick, from the Hands of EmpmckSy will meet with the Applaufe of every Phj- fician and Surgeon. Your kind Acceptance and Pro- tcftion of it, will be my greateft Honour? and a fuf- ficient Guard, from the Snarlings of invidious Cr/- ticks. I have the Honour to be, with great Refped, SIR, Your moft Obedient Humble Servant, 1®. 1749. SiL. OHalloran. (i) CATALOGUE O F BOOKS, Made Ufe of in the follow- ing Treatise. A. ACTA Medico-phylica Natur. L'Academie Royale des Sci- ences, les Memoires, Aquependente, Traite de la Chirur- • gie. Arciilaniis in Rhafin, a Boyle'$ ii Catalogue. B. Boyle's Philofophical Works. Borrichius, de fapientia -<^gyptorum. Briggii Opthalmographia. BriiTeau, Traite de la Catarade. C. Camper DifTertatio Medico-phyfica, / &€. Cnrtefii opera. Celfys. La Charriere, fa Chiriirgie. Chefeldon's Anatomy. Philofophical Tran fac- tions. D. Dionis Cours de Chirurgic. E. . Edenburgh, Medical Eilays. Catalogue. iii F. § Friend, Hiftoria Medicine. G. Gravefend's Mathem. Elem. N. P. Gaffendi opera. H. Harvey, de fanguinis circulat. Heifterus de Catarada & Glauc. Apolog. Tradat. Chirurg. Hecquetj fur Tutilite de la faignee, SCc. Hovius, de circul. humor, motu ia oculis. Hugenii Diop trices. I. Journal des Savans. Jefus, Hali opera. a z Kepleri iv Catalogue. K. Kepleri Dioptrices. L. Lemnius, de Miraculis Naturae. Litre, Memoires de TAcademie, Le Cat, Traite des Sens. Le Dran, fur les difFerentes manieres de tirer la pierre, SCc. Lewenhoeck, Philofophical Tranf- adions. M. Martin's Opticks. O Mara, Examen Diatribae Thorns WiUifii. Mery, Memoires de T Academie, fur la maniere de tailler de Frere Jaques. Mayernia, Praxeos Med. Molyneux, Philofophical Tranfac* tions. Morand, Memoires de TAcademie. Newton's, Catalogue. v N. Newton's,' Sir Ifaac, Opticks. O. Oribafiius Sinops Med. R Palfin, TAnatomie Chirurglcale, Petit, Phyfician, Memoires de I'A* cademie. Letre des reflexions, 6Cc. fur la vray fituation da Cryftalin. Petit, Surgeon, Memoires de I'Aca- demie. Plempii Opthalmograph. Porterfield, Medical Efiays of Eden- burgh. Pemberton, Diflertat. Medic, phyf. Ranby, ti Catalogue. R. Ranby, Philofophical TranfacSions^ Riverii Praxeos Med. Obfervat. Rolfoncius. Read, on Diforders of the Eye. Ruyfchii Thefaur. Anatom. Rohaulti Phylic. Renault's Entretiens phyfiques. S. St. Yves, les Maladies des Yeux. Scheuchezer, Ada Medic, phyfic. Smith's Optirks. T. Taylor, le Mechanifme du Globe de I'ceil. Syllabus of Diforders of the Eye. Winflow, Catalogue. vii w. W inflow, Expolition Anatomique. ... Memoires de TAcademie. Widelius, de Catarada. Woolhoufe, Diflertations favantes & critiques, fur la Catarade, &c. A PRE. A PREFACE. JF a luxurious Way of Ih- • ing, was the Rije, and is the Continuance y of fo many Diforders, to zvhich People are daily expojedy as Seneca has jujtly remarked ; Tern- perance, and an ahjtemious Way of li'oingj may certainly help to lejfen them. But tho' this DoBrine will hold good s in other Diforders, yet it will never anfwer in thofe of the Eye ; feeing that the b Poor X PREFACE. Poor are equally y if not more expofed to them than the Rich. It isy perhaps on this Account, that the Eye has feemed always to draw a more particular Attention from medical Writers. &ven from the Times of Hippo- crates, it has been handled with particular ExaElnefs* Nay fome imagine (i) that the Operation of a Cataradt was known to the Egyptians above three thoufand Tears azp ; feeing that Herodotus fays, that Cambyfes Jent an eminent (i) BoiTklilus de fapient. iEgypt. p. 20s. Heillcras de CataraCli, p. 286. PREFACE. xi eminent Oculift of Egypt, into Perlia, to cure Cyrus. Celfusy who was certainly no great Anatomift? has de- fer ibed the Catara6t fo ex- aBlyy and tfs Operation fo well (2)5 that zvhat has been fince writ on that Subjeth has been little better than a hare Tranfcription of his Words ; and neverthelefs he flourijhed in the Times of Tiberius> that is, immediate^ ly after the Birth of Chrift. Aetius was /lill more exact in his Dejcription of the b 2 Dijorders (i) Lib. vii. cap. vii. xii PREFACE. Diforders of the Eye. Hip- pocrates and Ceiius number about thirty Diforders inci- dent to this Organy .as the learned Friend (3) obferves ; and Galen a few more ; but this Writer recites above twice that Number of Dif^ eafes ; and their Symptoms and Curcy he "very accurate- ly defer ibes; and of which abo've thirty require manual Operations, Amongft the Greeks, next after Aetius, Paolus and Alexander cer-- tatnly "writ the be(l on thofe Diforders. But (3) Hillor. jSiccicinx, p. 139, 2 1 9, PREFACE, xiii • But the Arabians brought the Knowledze and Cure of thoje Dijorders mto much greater PerfeBion. Rhafis who praBifed Phyfick with great Applaufe at Bagdad, or Babylon3 about the Tear 90O5 wrote federal learned Treatifes ; and in particu- lar, in his Ninth Book, De Curatione omnium Parti- um, he treats "very largely of the Difeafes of the Eye. in his Eighteenth Chapter y he difcourfes of the Opthal- mia, and the different Spe- cies of it: In this Chapter nlfoj he gives ajuji, tho' con- fffe Anatomical Defcription of xiv PREFACE. of the Eye ; and particular- ly takes Notice of the Tunica Aranea^ which Jurrounds the Cryftalin-Lens. In the Thir- tieth Chapter, he gi'ves a large Account of the Cata- radtj and ifs Cure ; and de- fcribes the Operation with great ExaBnefs ; direBing the Needle to perforate the Eye, about three Lines Dif- tance from the Corneaj and leaves no Diforder of this Part unnoticed. Jefus Halij a learned Av^l- bick Phyftcian, wrote ex- tremely well upon the Dif ca- fes of this Organ ; thd the learned Friend? neither fixes the PREFACE. XV the Time of his JVritings, nor jyet gives any Account of his Works, only juft ohferves ; Sunt et alii au£}:ores Ara- bicij quorum libri extant, ut Abbenquenfit, Bulca- fem, Jefus Hali, Cam- manufali. Rabbi Mofes, &c. quos cum nihil me- morabile in fe habeant? et id mihi in animo fit, ut medicine potius, quam medicorum hiftoriam con- texam, filentio pr^ter- mitto." Hift. Med. p. He in fi fled, that all Cata- rafts were formed in the an- terior Chamber of the Eye; that xvi PREFACE. that is to fay, between the Cornea-Tranfparens and Iris ; and of Confequenee, that the Needle Jhould never perforate the Coats of the Eye pojteriorly. But if fays he, in the Operation y the Ca- tQiV^di Jhould flip between the Cryftalin and Iris, in this Cafe, the Needle may pafs into the pofterior Chamber of the Eye, and fo bring it hack, and deprefs it under the Cornea ; and in this Cafe, he affirmed, that the Pupilla was capable of a very great Difiention, which would im- mediately contra^ it f elf on the Removal of the Extra- neous Body, in the fame Manner PREFACE, xvii Manner as the Matrix does, immediately after Delivery. And to fupport this Ajfer- tioUy he affirmedy that were it between the Iris and Cryf- talin, it was impojfible to re^ move it, without affeBing this Party and of Confe- quencey depriving the Patient of Sight. By this it appears y that Aqiiependente was not the fir fi who affirmed. That it was impoffible to intro- duce the Needle into the pofierior Chamber of the Eye, without wounding the Cryflalin. This Opinion was alfo embraced by Albucafis and Mefue ; on the contra- ry y Azaravius, whom DoBor c Friend xviii PREFACE. Friend confounds with Al- bucafis, %vas of the contrary Opinion ; that is, that there were no Catara6ls5 but fuch . as were formed between the Cryftalin and iris. To reconcile thofe different Opinions, Arculanus, an emi- nent Phyfician of Verona in Italy ; and who, according to Friend, lived in the fifteenth Century y allows of both Sorts of Cataradls (4). He fays, that a Catarad: may be form- edin the anterior Chamber of the Eye, when the Matter, which (4) Arculanus in Expof. nonor. libr. Al*- manzoris. PREFACE, xix which Jhould nourifh the Du- ra-Mater, is 7iot in a good State ; or from too great an Abundance of it, or raoifi Exhalations. In all thoje Ca- Jes the Matter may tranfude thro' the Sclerotica ; and thus, by a Sort of Accumulation^ form a Catara6t hetvjeen the Cornea and Iris; and thoje in the pofterior Chamber of' the Eye? he thinks proceed from a Defluxion of Matter from the Pia Mater. Not to mention the num- herlefs Writers on this Part fence, as Riverius? Seiiner- tusj Rolfoncius, Plenipiusj ^(f. it has entirely employed c 2 the XX PREFACE. the Learned, fince the Be- ginning of the prefent Cen- tuiy. In thofe Difputes yWhich are related at large in the Beginning of this Work, the StruBure and Mechanijm of the Eye, were fo accurately handled, on both Sides, that it feemed impojfthle for any thing new to be faid on this Subjecf. Be fides this, not to mention the pretended Difcoveries of Nuck, and Ruyich. Hoviusj who af cribes the Merit of all thofe to hi?nfelf, has %wit an en- tire Book, barely to fie w the Circulation of the Humours in the Eye. 'lis this famcy who pretends to fhew the Choroides PREFACE, xxi Ghoroides compojed of fi'ue Lamin^5 or Membranes ^ and neverthelefs declares the Ca- tarad: to he a Memhrane.jor* med between the Cryftalin and Iris! Petit, formerly a celebra- ted Phyfician oj Namur, and fince of Paris, has pro- fejfedly laid himfelf out for Difcoveries in the Anatomy of this Part J and not unfuc- cefsfully. Winflow alfo has not been wanting for Difco^ 'veries in this, as well as in e'very other Part of the hu- man Body. Morand the Son, has alfo gi'ven Obfervations and Remarks on the Eye, and ifs xxii PREFACE. ifs DiJorderSj not unworthy of htmfelf. So has the lear- ned Profejfor Ferren? of Pa- ris, in bis Anatomical Lec- tures. Mr. Chefeldon has been very indefatigable in his Searches too ; and propofes a "very curious Operation, viz. the making an artificial Pu- pilla. Mr. Ranby, Serjeant Surgeon to his Majejiyy has likewije gi-ven fome Remarks on the Cataract in the Phi- lofophical Tranfa^lions for 1730. But be fides allthofejcarce a Winter paffeSy in which fome Thefes are not fuflai" ned at Paris^ Montpelier, or Leydenj PREFACE, xxiii Leyden? on this Subje^ : Tet are there jome on thefe Occa- ftonSy which Jhould not be forgot ; fuch is the Diflerta- tio Phyfico-Medica of Doc- tor Pemberton, addrejfed to the learned Do^or Mead; as alfo the Diflertation of Doc- tor Camper^ in 1744? on the fame Subje^. Be (ides an accurate Defcription of the Eye, and the Ufes of if s fe- deral Parts, according to the received Opinion ; ne alfo gives a Figure of the Canal Godronnee, of Petit ; as alfo a Defcription of the true Situation of the Eyes in their Orbits, contrary to the Opi- nion xxiv PREFACE. nion of a 'very celebrated Ana-^ toraift. By what has been Jaid, it will appear y how difficult a thing it is to write any thing new on this Subjetl. let 1 am "verj confident y that the cu- rious Reader will find fe'ueral Dif coteries well worth his Attention in the following Sheets. Be (ides putting an entire End, to the Difputes^ about the Seat of a CataraiS:? which thing alone, has been the Oc- cafion of great Contefis in the learned World, the diffe- rent Opinions, about a Glau- comaj PREFACE, XXV comaj and Cataradt, are alfo entirely confuted ; not by barely faying they were the fame ; but by examining the Opinion of each Author on this SuhjeB, and at the fame time (hewing, how he %vas de- ceived. Perhaps fome may think y that I have fpent too much lime on this Head; but I have been the more parti- cular in it, firft, to avoid the Criticifms oj People, who, though they might be convin- ced in their own Mind, yet, for the Jake of Contradi^ion, or to draw the Attention of the People on them, might be the Occafton, by taking up the Pen, of more unneceffary d phyfical xxvi PREFACE. phyfical Lumber : Secondly, becaufe it is a thing of juch necejfary Confequence to Man- kind in general y and in parti- culary to the pradical Sur- geon, to kno'Wy that all Opa- cities are at all rimes equally curable ; feeing^ that by this, he is not to wait for one par- ticular Time or Seafon ; or till the Fruit is ripe and fit to he plucked o^y as Su Yves pe- dantically exprejes it. As for the fmall Difference of Refratfion, between the Cryftalin-Lens and Vitreous- humour, 1 think I have evi- dently proved it, both from \ Opticks, Reafony and (which ■ is PREFACE, xxvii isjiill more convincing) indif- putable FaEis. I ba-ve aljo pretty manijcftly jhevon, that there is not any Adherence of the Ligamentum-Ciliare, to the CryftaliU'Capfula. Ke- plerus in his Dioptricks was the fir ft who ad'vanced, that the different Figures the Eye took, were occajtoned hy the Attaches of the Ligamen- tum-Ciliare, to the Cryftah'n. IhiSy tho it was a curious Remark for a Phyfician, (1 mean a Philofopher) was im- plicitly Jubmitted to, by all Phyficians, and Mathemati- cians //w^; na^fome (promp- ted by a laudable Zeal) went further, even to difpute with d a him xxviii PREFACE. bim the Difcoz^ery ; behi^ aJJmmed to jay, that Jo cw nous a Remark Jhould he made by any one, but an Ani- tomifl:. tloviiisV Book, I have ak fo examined ; not indeed out oj any Dejire of being thought a Critick, but barely to J ear ch out (if pojftble) the Truth ; feeing that the learned World are much indebted to him, for his Difcovery of the Blood- Veffels of the Eye; tho' in- deed, 1 believe y if People were lefs curious in enquiring into the firfi Caufm of Things, we fhouldfind Phyfick at a much greater Perfection than it now is ; PREFACE, xxix is ; feeing that fome Peo- ple Jhall Jpend whole Months, nay Tears too, to find out a Reafon, %vhy a Miifcle acls, the Heart eontraEis, or if Senfation be madey by the Ani- mal Spirits, or a vibratory Motion of the Nerves; and yet pall be often at a Lofs, to Jhew or defcrihe a Mufcle^ a Nerve, ^c. I have alfo given an Ac- count of this Operation, as it has been praBi fed by the mofl eminent Surgeons ; and ha^ue examined into the Merits of each of them, and pewed where they were deficient. J had indeed fome Thoughts , to have XXX PREFACE. ha^ve ghen an Anatomical Defcription of the Eye, and afterwards to have examin- ed the different Operations for a Catara6t ; in imitation of that celebrated Piece of J/.LeDranV(5); but be fides that this would confine me too much J from the general Re- marks, which are interfper- fed thro' this Work, Ifhouldbe alfo obliged to repeat fe-veral 1 kings y already f aid over, and over again : 'tis for thofeRea- fons, that I have publijhed this Piece, as you fee it ; leaving it to others to make life of the different Remarks on {5) Parallele des difFerentes manieres de tirer la pierre, &c. PREFACE, xxxi on the real StruEiure of the fever al Parts of this Organ, as by repeated Experiments I have found, and here defcri- bed them. 7he Method of differing an Eye, zvill, 1 flat- ter myjelj^ he not unaccep- table to the Curious ; feeing that by it every Man may ex- amine the different Parts of this Organ, and fee thofe Dif- coveries, which, by any other Method, could not be found out. As for the Cuts annexed to this Work, 1 took Care to have themfinifhed in the mo (I exaU Manner ; and in this my Trouble was fo much the greater, xxxii PREFACE. greater, feeing that I wa^ obliged (in order to (hew the Parts as they really were) to paint this Part in a Man- ner quite different from what it had been heretofore fepre- fented; and this 1 thought was the more neceffary to he done-ijeeingthat by oneGlanee of an Eye^ a Man ean imme- diately form a jujl Notion of this Part ; as alfo the more readily comprehend the feve- ral Remarks-, 8cc. interfper- fed thro' this Work In a fVord-, Reader, as my fole View has been nothing but Jruth-i fo 1 have f pared no Pains or Labour to come at it. 'lis upon this Account^, that PREFACE, icxxm that 1 hwve not once attempt^ ed to advance any thing with- out firft manifefily proving it ; and if 1 have Jometimes differed from fever al great Meny it has been only where Fa^s have obliged me to it, 1 have endeavoured thro' the JVbole, to convey my Thoughts in the moft clear and eafy Manner, without giving Of^ fence or Scandal fo any one, who has differed in Opinion from me. If then, it will pie afe the cu- rious Lovers of Truth and Cer- tainty, and encourage others to fear ch deeper into thofe Af- e fairs'^ xxxiv PREFACE. fairs, it will anjwer the In^ tent, for %vhich 1 purpofed it. Limerick, the i2th of Aprils I749» S. OH. I A N ACCOUNT O F T H E DISCOVERIES, d'c. Made by the AUTHOR, in the following Treatise. I.T^HE CataraB is, ever an Opa- A city, in the Cryjlaltn-body only. 2. The Glaucoma^ not a different Difeafe, but a different Name to exprefs this Diforder by. 3. Phcenomena confequential to this Operation, explained, 4. The Cure of a CataraSl fhewn. J, The different Motions, in the Globe of the £y^, occafioned by the A6lion of the Choroides Au" tericf\ X Discoveries^ '^c. 6* A Mufcle has different Degrees of CoRtra6tioii. 7. No Circulation of the Humours in the Eye. Anatomical Difcoveries* 8. The Iris compofed of Radial Fibres only. c^. The Vitreous-hu7nour^ not fur- rounded by any proper Mem- brane. 10. The Cryjlalm-Le?is has no Ad- herence to the Liga7ne7Uu?n'Ci^ Hare. 11. A Subftance, partly cartilagl^ nous and bo72ey^ in the internal Angle of the Eye, which I have called Os Opthal77ttcu77i. 12. The Origin of the Aqueous hii^ 7nour. J 3. Why the Eye is fubjed: to In- flammation, in Confcquence of couching. 14. The ■&• DiSCOVERIESj ^C. 14. The true Situation of the Cry/- falm-Lens^ and Choroides Ante- rior, I J. A Defcription of the Ltgamen- tum-Ciliare, 1 6> Koreotomy impradicable, as de- fcribed. 17. A different Method for perfor- ming this Operation propofed. ERRATA. Vage 32. line 3. for Parallel Rays, read Perpendicular Rays. P. 43 . /. ult. for Lamina, r. Laminae, OFT HE GLAUCOMA, O R CATARACT. I. f^'^m 1 HIS Diforder is, by the I Latins^ called Suffujio ; but it is more generally known by the Name CataraEia ; which, according to Livy^ fignifies GateSy or any other Obftacle to the Entrance of Towns, more efpecially fortified ones : Others will have it to be derived from x«TaVs«4 defluoy de-- labor J others again from K£g«*r, Cor- B nea 2 Of the Cataract. 7tea ; or, perhaps, from x*Ta contra «ai, Kogij, Pupilla, By Paulus^ and other Greeks^ it is called v^o'xv^w, lique^ facere. Others again diftinguifh be- tween a Suffujton and CataraB^ (i) in calling the Suffujton a beginning CataraEi ; and the CataraEi a C(?;^- Jirmed Suffujton, IL Bat, let it's Derivation be what it will, all agree, that the Ca- taraSl is, a Lofs of Sight^ with a Change of the natural Colour of the Pupilla, or black, into fome other Colour ; as for Injlance^ to white, gray, yellow, &^c. By this Defini- tion, or rather Defcription, it is ea- lily diftinguifhed from other Difor- ders, incident to this Organ. It is known from the Amaurojisy becaufe in it, the Sight is loft, without any Alteration in the Colour of the Pu- pilla *y (i) Praxeos Mayern in morb. intern, c. xiii. Of the Cataract. 3 filla ; from the Leucoma^ becaufe in this, 'tis the Cornea that is ren- dered opacous. From the Pterygion^ as it is a Membrane, that covers the Cornea tranfparens. It is known, from the Hypopyon^ as this laft is purulent Matter, colleded between the Cornea and /r/x, and jBu6i:uat- ing ; when, on the Contrary, the Opacity in the CataraB^ feems fo- lid, and behind the Pupilla. And here I fhoiild with a great deal of Perfpicuity, endeavour, according to Cuftom, to diftinguifh between this Diforder and the Glaucoma ; but as I fee very little Reafon ; (or rather none at all, as I fhall fhew prefent- ly) for fuch Diftindion, I fliall, with the Antients, efteem Glaucoma et WokI^lo. unum eundemque morbum ejfcy as OribaJiuSy Synvps, Med. lib, viii, remarks of them. B z III. But 4 Of the Cataract. III. But tho' the Fathers of Phy- fick, had called all Blindnefs with a Change in the Colour of the Pu- pilla^ indifferently, CataraBs^ or Glaucoma s ; yet Experience fatisfir ed their Succeffors, that there was a great and eflential Difference be- tween them : the one being a Dif* order, which admitted of a Cure, by the Operation ; and in the other, the Operation ferved only to remove the Deformity in the Eye, without adding any thing to the Sight ; which Orihajius alfo remarks, by faying, Glaucomata omnia^ curationem non recipiunt^ Sec. And as thofe Opa- cities which they found irremediable, feemed moftly of a grayifh blue, or Sea Colour \ they only were called Glaucomata a v>^a6KoJ An.: _ and Of the Cataract. 2^ and could not be removed^ or fup-^ freffed\ and therefore the Opera-r tion did not fucceed : Another fuch-r like Operation^ performed by Bor- 'teliusy was equally unfuccefsful^ on the fame Account. XXIV. Now it is evident, that there muft have been, an Opacity of the Cryjlalin-Lens in the above Cafes ; or, for what Purpofes would they have paffed the Needle ? And if fo, how could the Opacity of the Vitreous-humour fhew itfelf thro* this Body, when it refufed Admit- tance to the Rays of Light from ex- ternal Objedls ? If it were the Vi^ treouS'humour only which was af- feded, as he feems to think, it fhould rather (in order to render it opaque) exhibit fome other Colour, thro' th^ Pupillay than a tranfparent, or plear Glafs-colour, which every body knows to be the true Colour of this Humour^ in a found State of 34 Of the Cataract; of the Eye ; and yet I am fure, no body will pretend to guefs at it's Colour, by looking thro' the Pu- filla : With how much lefs Reafon^ then, fliould we judge of it's Alte-' ration in a morbid State ? XXV. But, becaufe the learned Author obferves, that the CataraEiiB fplendentes^ &^ lucent esy may be al- ways ranked amongft the Glaucoma-' tjCiy or incurable CataraEis : I re- mark, that, not only Pare diViAAntoiney. ^c. give Inftances of the Cure of fuch CataraBs ; but alfo, that St. Xves (5) exprefly fays, that " the Sky-coloured, thofe of a Aiming Silver, fomewhat like clear Glafs ; and thofe of the Colour of Sea- water, fucceed beft, next after the Pearl-colour." XXVI. As to Taylors Diftinc- tion, I only obferve, that Petit the Phyficiaa (5) Les maladies de yeux, chap, xviii. Of the C AT AR ACT, 2 5 Phyfician denies any Connexion, or Communication, between the Ojf- talin-L,e7is and it's Coverhig ; and that in all States of a Catai-aEi he has conftantly found this laft tranf- parent. Memoir es de P Academic des Sciences y 1730. He alfo af- firms, that in every State of a Ca- taraSi^ whether hard or foft, of a long Standing or (hort Duration, he has conftantly found the Cryjlali?i' Lens fmaller, than in it's natural State. (Sa letre contenant des refle- xions^ fur ce qui M. Hequet d dit^ touch ant les 7naladies des ^eux^ p, 16.) And I dare be bold to af- firm, that all who are acquainted with the Writings of that great Man, will take his Word for it. XXVII. But St. Yveis Opinion, is certainly the moft ingenous : He defines a Glaucoma to be a CataraEi^ complicated with a Gutta Serena ; and in this Cafe, it is manifeft, that E de- a6 Of the Cataract, depreffing the opaque Cryjlalm^ can no way contribute to the reftoring of Sight ; becaufe the Amaurofis alone is pSf^petual Blindfiefs, But if you mind his Words, you will find, that he had no more Experience for what he advanced^ than the Gentlemen his PredecefTors. He remarks, " that by a careful In- " fpedion into Eyes attacked with " this Diforder^ he found a fort of " Alteration in the Cryjlalin^ which *' fupervened to a Palfy of the Gi- " liary Nerves.^' Now it is. evi- dent, by his own Words, that thofe Obfervations were made, on People already attacked with a CataraSi ; and in this Cafe, how could he ob- ferve. this previous Weakilefs in the Mufcle of the Iris f And as to the Dilatation of the Pu^illas we all know, that the v/eaker the Impref- iidn, which the Rays of Light give to the Choroides, the greater is the Relaxatiori Of the Cataract, ay Relaxation of this Part, See N. LXVII. CoRkoLLARiuM I. From what has been faid then, it is evident, that the Difputes about the certain ■Seat of a CataraEt^ are entirely re- moved : Difputes which havd toolong ^employed the learned V/orld ; feeing ■that if they had but confidered, the true Situation of the Cryjlalin'-Lens and Iris\ a very great deal of Time, Labour, and Paper, might have been faved ; but yet fomewhat of greater Confequence, than all this, particu- larly advantageous to Practice, may be drawn from the Above. CORROLLAR. II. As tllCU, all Ck- taraEis are Opacities of the Cryfld- lin-Lens ; that the Glaucoma is but a different Name, for the fa?ne Diforder ; and that all Suffufions of the Cryflalin-'Le?is are remediable, it neceifarily follows, that all Cata- E 2 ?'aEls a8 Oj the Cataract. raSis are equally fo. And we do af- firm, that all Opacities of the Cryf- talin-Lens^ whether hard^ foft^ or in whatfoever other State, are equally curable^ by an Operation which we Ihall prefently {hew ; provided they be not complicated with a Gutta Se- rena ; which no Author, but St. Tfves takes Notice of ; and indeed, he fhould fir ft have produced fome Inftances, to fupport that Opinion, in order to gain it Credit : But I could produce an Inftance in this Town, of a Woman who had a ca- taraElous Eye^ in which the Ins had very little perceptible Motion ; and which Taylor had declared i7i- curahle ; which I neverthelefs rejio- red her the \}{^ of the Twentieth of March^ 1749 ; but that I think, what has been faid, is fufiicient to fatisfy any Man, who feeks after the Truth. CoRROLLAR, Of the Cataract. 29 CoRROLLAR. III. From the Fore- going alfo, the true State and Con- iiftence of a CataraEi may be found : Thus, for Inftance, if it be more elevated in it's Cejttery than in it's Circumference^ we may affirm the Cryjlatin to be hard : If flat, or de- prefl^ed in it's Nucleus^ we may con- clude a Solution of Cojitinuity in the Parts of it. If it feems more pro- minent, or jetting out in the infe- rior, than the fuperior Part of the Pupilla^ we may fay, it , is a fofty or milky CataraEi. XXVIII. Now in the Cafe of a Glauco7?tay CataraEi^ or Opacity of the CryJialin-LenSy the Intentions of the Operation, are, the deprejfmg of this opaque Body^ by Means of which, the Rays of Light will have a free Ingrefs to the Bottom of the £3/^, and Sight be reftored. But as the greateft Succefs we can promife ourfelves. 50 Of the Cataract. ourfelves, from the Needle^ is, to give the Patient fome feint Notion of Colours, and Light fufficient to dired him ; and even this is fo un- certain, that fometimes it fliall be but inftantaneous ; fometimes fhall continue for a Month or two, or lon- ger; and butvery few Inftances, where it has remained, with even this fmall Degree of Strength, for any con- fiderable Time. From thence, the great Uncertainty of Succefs, iii this Operation^ even in the moft promifing Cafes (the Truth of which the beft Authors acknowledge) it may be debated, whether it had not been better, to be entirely laid afide ? And indeed it feems to be fo, by the moil: eminent Sur- geons ; who do not care to hazard their Charadiers, on an Operation^ from the Succefs of which only. Peo- ple judge of the Abihties of the Performer. Tho' indeed it has this to recommend it, (as the learned Hei- Jler Of the Cat ARAcT. 31 Jier ]u{\ly remarks) that to a Perfon weli-inftru(5ted in the Knowledge of thofe Parts, there is not the leaft Danger to be apprehended. XXIX. This fmall Degree of Light, which the Patient has, after the Operation is well-performed, has very much puzzled Phyjicians and Mathematicia7ts^ to account for '5 However, they have done it thus ; ^ It is a Principle of Diop- T RICKS, That, Rays of Light ^ paf- Jing from a rarer^ into a 7nore denfe Medium J are refraBed^ acceding to the Perpendicular, Now the Rays of Light, paffing thro' the Air, from a luminous Body^ to the Hu~ mours of the Eye, which are a den-- jer Medium^ are here refraded, or broke in their Direction ; and this Power of converging the Rays of Lighty is ftill greater, in Proportion to the Denfity of the Body thro' which they pafs. However, it is to be g a Of the Cataract, be nbticed, that this Law only re- gards thofe Rays, which fall in an oblique Diredion • becaufe parallel Rays, pafling thro' different Medi- ums^ fuffer no Refraction ; feeing there is no Obftacle in the Body, thro' which they pafs, that fhould incline them, either to the Right, or the Left ; therefore they keep their priftine Diredion. XXX. Now, this being the Cafe, if the Rye was filled with the Aque- ous-humour only, the Rays of Light would be converged to a Point con- fiderably beyond the i^^//;^<3; (6) . It was therefore neceffary, that fome other Body, of greater Denfity than the former, fhould be interpofed, in order to unite thofe Rays, in a Point nearer the Retina : To which Pur- pofe, the Cryjialin-Le7ts wonderfully anfwers ; (6) Martinis. Opticks, Smiths Principles of Opticks, and Dr. yurin\ Letter, ^c. Of the C AT AR ACT. 3 3 anfwers ; which, by it's Convex- figure, ferves to unite the Rays foon- er ; and therefore, paffing thro' the VitreouS'hmnour^ which is of lefs Denfity than the former, and of a Concave-furface, the Rays muft be ftill more converged^ fo as to unite upon the Retina, XXXI. If then, by any particu- lar Idiofyncrafy^ the Cryjialin be rendered opaque ; when displaced by the Needle^ the Vitreous-humour fills up it's place,- and neceflarily forms a Convexity in it's anterior Part, by the lateral PrefTure of the fuppreffed Cryjialin, But as this is a rarer Medium^ than the Cryjialin^ of Confequence, the Rays of Light are not fo ftrongly converged ; their Focus is therefore beyond the Retina^ and Sight Jhould be conjufed. XXXII. But, becaufe a great ma- ny objed, againft the antient Doc* F trincj 34 Of t^^^ Cataract^ trine, That, if the Cataract was^ a Ivlembrane formed in the Aqueous- humour ; after depr effing this Mem- brane, the Patient fhould fee^ as well as ever y feeing, that there was g no other Obftacle to their recoverin Sight. But it is evident, that they, who make thofe (as they call them) unanfvverable Objections, are not acquainted with the antient Doc- trine : For the Aittients taught, that as the CatdraSi was formed by the more denfe or folid Parts of the Aqueous-humour^ accumulated ; yet tho' this Membrane^ or, accumula- ted Matter^ were fuppreffed. Sight was ftill imperfect ; becaufe the Rcr mainder of the Aqueous-humour ^^ had loft it's more denfe Parts ; the RefraEiion^ therefore of the Rays of Light, was not fo great, and Sight was proportionably weak. This I mention, not that it is any way ne- ceflary to our Difcourfe, but barely to fhew, how juftly the Antient s reafoaed y Of the Cataract. 35 reafoned ; and at the fame time, that the Sentiments of all Parties^ with refped to this Diforder^ might be here explained. XXXIII. But it is to be remark- ed, that the mofi: exa6t Opticians ^ have found this Difference of Re- fraSiion^ between the Cryjlalin-Lens and Vitreous'-humour^ fo inconceiv- ably fmall, that it is fcarce difcer- nible (7). Their Difference, as to Denfity and Spectjick-gravity^ is but fmall. If then, the RefraBion of the Rays of Light, out of Air into Diamond^ (the moft denfe Medium) is, according to the niceft Obferva- tions, but as Jive to two ; how very fmall then muft it not be, when paf- fing from the Cryflalin-Lens to the Vitreous-humour ? io finally that the learned HeiHer (iri Dijjertatione de F I Amauroji) (7) Kepleri Dioptrices, Newton, de.k Hire, 5 6 Of the Cataract. j^maurojij thinks, ths.ttf)e Refoluti* on of the Vitreous-humour into Wa- ter ; (8) and even that of th^CryJia- lin-Lens too (9) ; are nor alone, by their Rarity^ fufficient to caufe a Gut- ta Serena. But can any thing more manifejily fhew, the very fmall Dif- ference of RefraElion^ between thofe two Bodies, than the iimple Experi- ment of Hu GENIUS, Dioptr,Propof, 31? Who, by forming an artificial Eye^ with the fame Size of a natu- ral one; and filHng it, with Water only, had the Images, from exter- nal Objeds painted on it's Bottom. See further Improvements on this Machine, in Heifter de Catarada, Fol. 137, &^c, XXXIV. But thofe our Argu- ments are unanfwerable, if we re- flecl: (8) L' Anatomic Chirurgicale de Palfin, p. (9) Rolfgncii Piffertat. Anatom. Jib. I. cap. xiii. Of the' Catar A<3tK 97 fledt on the noted Inftance of ^/^r^^<37/ Petity the Father ; ( i ) who tells of a Man, in whom the opacous Cryjlalin had pafied into the anterior Chamber of the Eye^ which Body he extrad:ed^ by opening the Cornea ; and never- thelefs, this Man could fee with the fame Force, that People generally do, after deprefilng the CataraSi, St. Tves (2) relates two or three more fuch Hiflories, in his own Pradice. Now, if the above Hypo- thefis (N. XXIX.) were- true, this Man fhould not fee at all ; becaufe, befides the Vitreous-humours beings a rarer Medium^ (N. XXX.) the CryJ^ tahn-Lens is alfo taken out, and the Eye has not it's full Convexity, And in this Cafe, the Rays of Light fhould unite at a Point, CG7ifiderably beyond the Retina : The Faljity of which, (i) Memoires de I'Academie Roy ale des Sciences, 1708. ■1(2) Les maladies de yeiix, ch^p. xxi. 3 8 Of the Cataract, whichj thofe Inftances manifejlly prove, XXXV. But, becaufe the ingenu- ous Dr. Porter field (3) fhews the ImpoflibiUty of a Man's feeing well, after depreffing a CataraEi^ from the Difference of Texture, in the Body of the Cryftalin ; it being more fohd in it's Center^ than in it's Circumference ; and of Confequence, that the Light fhould here fuffer a greater Degree of RefraSlion, This Mechanifm the DoSior thinks was neceflary ; becaufe, otherwife, the Rays, palling thro' it's Circumfe- rence^ would meet at a Point nearer the Retina^ than thofe which paffed thro' it's Center ; the Light in this laff Cafe, running a fmaller Space. This Objedion had been made to me, before I faw the DoElor\ Second EJfay^ by Dr. Camper^ 2l very inge- nuous (3) Medical Effays of Edinhrgb, Vol. IV, p. 152, ^f. Of the Cataract, 59 nuous Phyfician of Leydetiy and who has particularly applied himfelf to the Study of this Organ, XXXVI. But to this, I anfwer, that if we confid^r, that the Cen- ter of the Cryftalin, is always pa- rallel to that of the Pupilla ; we will find, that the Rays of Light, which fall on this Part, fuffer no Refrac^ tion, (N. XXIX.)— From all which, I think, we may juftly conclude, Firft, 7*hc^t the Reafon-i why we fhould not fee better after the Operation, (not to mention, the Uncertainty of it's fucceeding in moft Cafes) has not yet h^en fuffici^ntly known. Se- condly, That the Cryftalin-Lens no fur^ ther contributes to Sightj but by it^s Tfanfparency^ and ferving as a Me- dium, to preferve the due Convexity of the Eye. XXXVII. But 4P Of I the Catara ct. XXXVIL But . tho.fe Corrolla- rks, will ftill appear more ?nanifejl^ if we coniider, what numberlefs Experiments have fatisfied me of: viz. 7X^/ //6^Cryftalin-Lens, in moji Sorts of Aiiimals^ (Men, ^r.) of the fame Species and Age, is gene^ rally of the fame Weight, Convex- ity and Diameter : Thus, for In- flance, in Men^ it is about four Grains; in Youth^ two Grains, |, or three Grains : In Sheepy about twenty Grains, in Bullocks^ forty, and fo on. But the Vitreous-hu^ mour^ never preferves this Regulari- ty ; for, in the two Ryes taken out of^ the fame Head^ you will find a great Difference^ with refpedl to their ^luantities ; one Rye containing, fometimes a Third more than the other y fometimes lefs ; but rarely^ the two Vitreous-humours of the Came A?2imal are, alike heavy. XXXVIII. Of the Cataract. 41 XXXVIII. Lem7nus (4), as alfo Borelliy have obferved, that we fee better with the left Eye^ than with the right ; and indeed, in general, this Obfervation is true : But M. LeCat (5) denies it to be conflantly fo ; becaufe, fometimes (as he fays in his own Cafe) the right is the beft lighted. This Phcenomenon fome have accounted for (6), from the different Partings of the two Caro- tid-Arteries : The left, arifing im- mediately from the Aorta ; whilft the right Parts, from the r ght Sub^ clavian ; and of Confequence, the left Eye is better and fooner fupplied. But this cannot be a fatisfadory Reafon, even tho' the left £)/^ were always the beft fighted. This D f- proportion then, in the Vitreous-hu- G mom ^ (4) De miraculis occultis nature, p. 371. (5) Traite des fens. (6) Les Eatretiens phyfiqiies de Pere Reg- nault. 42 Of the Cataract. mour^ evidently points out the Rea- fon of this Appearance. XXXIX. This Difproportion of the Vitreous-humour^ very naturally explains, the Caufe of the Pr(zjhitce^ or long-lighted ; and the Myopes^ or near-lighted. Thofeare generally ima- gined, to proceed from the too great Convexity of the Cryjlalin-Lens^ in the latter Cafe ; by which Means, the Rays of Light, from diftant Objeds, unite, before they arrive at the Retina ; or, from too great a Flatnefs of this Body, in the Prcef- bitcBy on which Account, the Rays from near Objeds, have their Focus y bevond the Retina. But as thofe different Figures of the Cryjlalin^ are only imaginary ; and that, the too great, or too fmall Quantity of the Vitreous-humour^m different Eyes of the fame Species (N. XXXVII.) is manifefly we think this laft more evidently Of the Cataract. 43 evidently to account for thofe Phce^ nome?ta. XL. Having then, I think, evi- dently proved, the very fmall Dif- ference of RefraBion^ between the Cryjlalin-Lens^ and Vitreous -hu- mour ; too fmall, to occaflon that very fmall Quantity of Light, which People enjoy, after precipitating the Cryjlalin : I fhall now fhew, by the fame Force of Arguments, and Fad:s equally convincing^ the true Reafon^ why we do not poffefs bet- ter Sight, after deprefiing the Cav- iar aEi ; as alfo propofe an Opera- tion, by which a Perfon, in any State of a CataraB^ shall see, pretty nigh as well after the Operation, as if no such Disor- der HAD EVER happened. XLL The Vitreous-humour is co- vered, by a very fine Membrane^ which is compofed of two Lamina : G 2 At 44 Of the Cataract. At the Cavity or Socket of the Fi- treouS'humour^ in which the Cryf- talin-Lens is lodged, thofe Lajniita leparate ; the internal Covering, the Cavity ot the Vitreous-hufnour ^ and pofterior Convexity of the Cryf- tali?2-Lens ; v^hilft the external La- men^ furrounds the anterior Part of this Body ; by which Mechanifm, the Cryfialin is firmly attached to the Vitreous-humour, It is remark- able, that the anterior Part of this Membrane, is much thicker than it's pofterior Part ; and this M. W inflow feems to think (7), pro- ceeds from fome Expanlions of the Retinay over this Membrane. Mor- gagni has obferved, that the inter- nal Surface of this Membrane, is conftantly humedled with a clear Lyfnphatick-Water \ and Petit the Phyfician (8) denies any Communi- cation (7) Expofition Anatomiqiie, Tom. IV. (s) Memoires de I'Academie, 1730. Of the Cataract. 45 cation between this Membrane, and it's interpofed Body, either by Blood- Veffels, or otherwife ; but that this laft is nouriihed, by abforbing the Lymph furrounding it. XLII. This Lymph is fuppHed by a particular VeiTel, which piercing the Eyey with the Optick-Nerve^ paiTes obhquely thro' the Vitreous- humour ^ and furrounds the pofterior Part of the Cryftali7i-Leiis \ giving very fine Ramifications, which creep into this Body, and difcharge them- felves there. Petit the Phyfician, has conftantly found this Lymph to exift, as well in a morbid, as a found State of this Organ. — We have often Inflances of CatarGBs fubfiding of themfelves ; of this May em (9), and 6 Mara (i) give cv/o notable Hiftories : This happens, when the Cryftalin has acquired a folid Con- fiflence ; ■ '(9) Prax. Mayern. cap. xiii. (i) Hiltoris aliquot medicas rario res, p. 174. 46 Of the Cataract. fiftence ; and by continually pref- fmg upon the inferior, and late- ral Part of the Capfula \ which is leaft capable of Refiftance, it at length, gives Way, and the Cryjla- I'm flips thro' the Opening by this Liquor's lubricating the internal Sur- face of the Capfula, XLIII. The Strudure of this Membrane, being thus defcribed. The Needle being introduced, and the Capfula perforated, the Cry (la- Ihiy by a certain Encheirefs^ is thrown out, and deprefled, under the J^i- treouS'humour ; but it's Membrane, or Covering, ftill remains, being a Continuation of the Vitreous-tunick, Now this Capfula^ being a Part en- dued with a great Elafticity, imme- diately after retraces itfelf, and co- vers the now convex Vitreous-hu^ mour, XLIII. If Of the Cataract. 47 XLIIf. If then it happens to be ftill tranfparent, the Light may pafs thro' it, (fhrivelled as it is) for fome time ; but as thofe very fine Capil- laries^ which part from the Vajcular Circle of the Iris^ to ramefy upon, and nourifli this Membrane, are, by this Means broke, it is rendered opa- cous, and of Confequence, light, very much obftrudled. And it is this Membrane, thus pierced, which Maitre''Jea7i- calls by the Name of an Appendix^ or Excret fence of a CataraSl. It was this al- fo which occafioned thofe ragged Films, which our learned Country- man, the Honourable Mr. Boyle (2) obferved in a Mafi after couching a CataraEi. But then it may be de- manded, whv thofe Filaments are not oftener obferved ? To which, I anfwer, that it depends, fir ft ^ on the Skill of the Operator, in not hacking (2) Philofophical Works, Vol, III. p. c^^^. 48 Of the Cataract. ^ hacking this Membrane too much : Secondly^ on the Quantity of the opaque Body deprefl'ed. For if it be not much diminifhed in Bulk, the Eye lofes nothing of it's Con- vexity ; and of Confequence, this Membrane has not fufficient Space, to float in the Eye. XLIV. Now in examining an Eye, upon opening the Cornea tranf- parenSy and prefling on the Ball of the Eye, the Tunica- Ara7i(za is broke, and the Cryjlali7t immedi- ately difengages itfelf and pu flies it- felf thro' the Aperture in the Cornea, By this Means, it's Membrane lies on the Socket of the Vitreous-humour^ unregarded by reafon of it's great Tranfparency ; tho' mofl: who have difTeded an Eye this Way, have found fomewhat like Hairs in the Vitreous Cavity^ which were nothing elfe than the Folds of this Mem- brane. Perhaps, it might be fome fuch Of the Cataract. 49 fuch Appearance, which occafioned the learned Brigs (3), and fome other great Men, to deny the Ex- igence of any fiich Membrane : But it certainly, not only exifts, but is alfo of much greater Denfity, than is generally imagined ; feeing M. Wi7tjlow (4) has been able, with a common Scalpel, to fnew it com- pofed of two Lamina^ with a Sort of Cellulare Sabftance interpofed. XLV. But if you infafe an Eye, for thirty or forty Hours, in Spirits of Wine, or any other Acid-Men- Jlruum^ and after examine it, as above, you will find a whitiili Sort of Opacity, in the P'itreons-Cavity ; which is occafioned by this Liquor's rendering, the Humours of the Eye more folid, and opacous, and their Membranes denfer. Now in exa- H mining (3) Opthalmographia, p. 16. (4) SonExpofitionAuatomique. 50 Of the Cataract. mining the Eye of M. Bourdelote^ (Vide N. XVII.J the clouded Body, which was obferved in the Vitreous- hmnour ; and which Brijfeau^ and after him Heijler concluded to be a Glauco7na^ was nothing elfe, than the 'Tunica-ArancBa contrad:edj and no Doubt, a little ofFufcated too. To the fame Caufe, we affign what Scheuchezerj Phyfician of Zurich in Swijferla?2d^ relates (5) of a Wo- man, whofeCriy?^/m was depreffed; and upon examining this Eye after Death, the anterior Part of the Fi- treous-humour was found thick and clouded. XL VI. To the fame it is, that we attribute, what Morand^ the Son, gives to St. Yves (6), in relation to two CataraBs^ which he depreffed in a Soldier of the hivalids. In . each (5) A6la Medico-phyfica Nature Curiofor, Tom. III. Obf. 36. (6) Reponfe a line letre critique de M. Mou- chai'd, contre fon traite des maladies des yeux. Of the Cataract, 51 each Eye, he found the Cryjlalln^ lodged under the Vitreous-kumour ; and this lafl: convex in it's anterior Part. This (it's anterior Part) he found, covered with Specks of a whitifh Colour, in each Eye ; and thofe Specks he imagines might be occafioned by the Cicatrices of fome Scratches, which the Needle might have made in the Operation. St. Yves thinks, thofe clouded Specks proceed only from CataraEis^ which have been deprefled before full ripe ; and fo are hacked and cut to Pie- ces, in the Operation : Nor is he at all furprifed, to find in operated Eyes, fome times Menibranoi-i-s-Jhreads^ which he attributes to the fame Caufe. XLVII. It is a little furprizing, that three fuch great Men, as JVi?i' Jlow^ Petit and Merand^ who were at the Examination of the above Eyes, vv'ould not enquire more par- ti 2 ticularly 52 Of the Cataract. ticularly into the Caufe of them Opacities, which they obferved in each Eye. Had the great Winjlowy but remembered, the beautiful De- scription he gave of the Cryjialin- Membram^ it's Denllty, Elafticity, fePc. or Petit but recollecfied, the great and ufeful Difcoveries he made, with refpecl to this Capfula^ and it's contained Body, they would hav^ quickly feen, the Caufes of them opaque Bodies ; by which Difcovery, joined to their great Knowledge, in the Structure and Make of thofe Parts, we fbould perhaps fee, this Operation, in greater Credit, than it now is : Since it is evident, from what has been already faid, (N. XXXIII. ad XL.) That, if a Me- thod was found out, to take away the Capfula with the opaque Cryjla-* lin^ WE SHOULD SEE PRETTY NIGH AS WELL, AFTER THE OPERATION, AS IF NO such' Disorder had ever HAPPENED. XLVIII, Of the Cataract. 53 XLVIII. From the Strudure of thofe Parts, fuck an Operation feems feafible, and not to be attended with any Danger. Firji^ by a Difcharge of Blood, which by diflurbing the Humours, might deftroy Sight; be-* caufe the very fine VelTels, which the Choroides gives to the Tunica- Arancea^ contain but the fercus Part of the Blood ; fo that wound- ing of them is not attended with the lead ill Confequence. Nor is there more to be feared from the Blood- VefTel, which piercing the Eye, with the Optick-Nerve^ fpreads itfelf over the Retina ; begaufe, beyond the Middle of the Vi- treous^humoiir^ it's Expanfions are but mere Limphaticks, XLIX. However, I mufl not omit mentioning, that I once fLewed, the pofterior Part of this Membrane entirely ipread over, v/ith Blood- VelTels. 54 ^/ the Cataract. Veffels. They took their Rife, by fome little Branches, from the Liga- me?2ttim Ciliare ; and by others, from the Artery of the Retma ; and uniting into one Trunk, ramified themfelves differently, all over, the pofterior Part (only) of this Mem- brane. I took of this Membrane with a great deal of Care, and Cir- cumfpedion ; and tho' I imagined, the Cryftalin-^Lens did not come out, with it's ufual Facility ; yet could I not conclude, from thence, that there was . any Communication be- tween the Cryfialm^ and it's Mem- brane ; becaufe, upon examining the former, even with a good Glafs, I could not perceive any thing that feemed like a Blood- Veffel, in this Body. L. The Method I took for this (and which I think is more certain, and occafions no Difputes, which it is imagined, Injedions often do) was. Of the Cataract. 55 was, by hanging a young Dog, by his hind Feet, to a Poft : In about ten Moments after, I could perceive the Blood- Veflfels of the Eye, become more manifeft. 1 then got an Affif. tant, to hold his Head firm; and with a convex Needle, took up both the Jugulars. By this Means, the Blood was intercepted, in it's Return to the Heart ; and of Confequence, all the Blood-VeiTels filled up. i he exad; Figure of this Blood- VejfTel, as it really appeared, I have caufed to be engraved, in one of the Plates annexed to this Work, S^QPlateW. LI. This Experiment, juftly ex- plains, a Phcenonienon^ which has been often treated of. People ima- gine, fometimes, that they fee Hairs, or fome opaque Bodies, fwimming in the Air, which hide Part of an Ob- ]ed from them. To explain this Appearance, fome have had Recourfe to ^6 Of the Cataract. to spots on the Cryjialin^ which refufe a Paffage to the Light. But as it certain, that People who com- plain ot this Diforder, have the Gryftalin clear (for it is impoffible, that there fhould be an Opaci- ty in the Cryfialin^ without it's appearing fo, to a Spectator) it is not a fufficient Reafon. Others have had Recourfe to too great a Dilatation of the Blood- Veffels, on fome Part of the Retina, But as the Retina is always plentifully fupplied, without any Inconvenience to Vifion, we rejed: this Reafon al- fo. The pofterior Part of the Cryf- taliji-Capfula^ in a natural State, re- ceives it's Nourishment, by L,i?n- ph a ticks : If then it happens, that pure Blood is forced into them, in whatfoever Part it lies, fo much of an Obied, will be certainly hid from us. Nor is this Explication other- wife worth mentioning ; but be- caufe it fhews us, a Means to remedy this Of the Cataract. 57 this Inconvenience ; which is, by plentiful Bleeding, in the Jugular- Vein, purging, and a diluting Diet, which lefTen the Quantity, and at- tenuate the Vifcidity of the Blood; and fo hinder the fanguineous Points from coagulating in thofe very {len- der Tubes. LIT. In the NyBalopia^ the Pa- tient is quite blind in the Day-time ; but towards Evening, begins to dif- tinguifh Objects ; and after Night- fall, fees pretty well. This Phanc^ menon may be thus explained : In the Day-time, the Pupilia is con- traded, fo that the Blood, which is forced into the ILimphatkk-Vejfels^ and which principally fpreads on the Center ot the Capfula^ ftops a Paflage to the Light ; but in the Night-time, when the Pupilia be- comes more dilated, the Light paf- fes thro' the Sides of the Cryjlalm ; and is the Reafon why, fuch Per- I fons 58 Of the Cataract. fons fee beft in the Dark. But to this, I own, there may be an Ob- jection made, which I cannot an- fwer ; nor would I have any one form a Method of Cure, from fuch a Principle^ left it might be errone- ous. For, as the Contraction and Dilatation of the Puptlla^ are in Proportion to the Impetus^ which the Rays of Light imprefs, on the Choroides-pojlerior^ it will confe- quently follow, that, when the Rays of Light caufe no Senfation here, the Pupilla fhould be in a State of Inaction, that is, quite dilated (N. LXVII.) This I mention, to fhew, how dangerous it is, to adhere to any Theory, how probable an Air of Truth foever it carries with it ; more efpecially, when we would endeavour to make our Pradiice co- incide with it. — But to our Subjedl. LIII. Nor from the Parts, enga- ged in the Operation, is there more to Of the Cataract. ^^ to be feared. It is true there is fome Connexion, between the /r/>, and Vitreous-Membrane^ by Means of the Indentations of the Procejfus-Ci- Hares ^ on this Part. But it is to be obfer- ved, that thofe Notches are below the Cryftalin ; and even tho' they were not, yet if, what they call adherent CataraSis^ are fuccefsfully feparated from the Iris (fee Pare^ Brijfeau^ Antoine^ &c.) without any dange- rous Confequences enfuing ; fure then, there is much lefs to be ap- prehended here. LIV. But becaufe the ingenuous Dr. Porter jield^ already mentioned, endeavours to fhew, that the diffe- rent Figures which the Eye takes, is occafioned by the Attaches of the Ligament um-Ciliare to the Cryfta- lin- Lens (7) ; and of Confequence, I 1 that (7) See alfo Keplenis^ in his Dioptrkks^ Mar- tin^ PemhertoHy Gravefend^ and mod AuthorSj who have wrote on this Subject. 6o Of the Cataract. that People, after couching, have not that FaciUty of altering the Fi- gure of their Eye, for different Ob- jeds. I obferve, that there is not any Attaches between thofe two Bo- dies, more th^n what has been, al- ready, taken Notice of, (N. XLVill.) at leaft, by any Experiment that we can make : For, if you perforate the Capfula^ and pufh out the CryJ- t(iIm-Lens^ it's Membrane immedi- ately covers the Vitreous-humour : which fure, it cou^d not do, were it any ways attached to the Ciltary- Ligamefit. Or, if, after ftripping off the Sclerotica^ you divide the Ch oroides all round, below the Li- game?2tu7n-Ciliarej and pierce the Arancea^ fo as entirely to feparate this Membrane, from the Vitreous- tunicky and then pufh out the Cryf- talin^ yet ftill you difcover np Ad- herence. LV. But 0/ the Cataract. 6i LV. Bat becaufe, to prove a Thing of this Confequcnce, a Man ean never be too exad: in his Expe- riments : I remark, that fuch an Adherence is quite impoffible, from the different Situations of the CryJ^ talin-Lens and Ljigamehtum-Ciliare, This lafl: being, the pofterior Part of the Procelfus-Ciliares ; which Pro- ee/fus cover, and in fome Shape adhere to, the anterior Part of the Vitreous-hu7nour^ vi^ithout touching the Cryjlalin-Capfula at all. If then the ProceJfus-CtliareSy which are three or four lines nearer the Cryjlalin^ than the Ligaynentt^n-Ciliare is, have no Adherence to this Body ; with how much, then, lefs Appearance of Reafon, can we fuppofe an Ad- herence, between it, and the Liga- ment um-G Hare P And by which alone, we would pretend to explain the different Figures which the Eye takes, LVL As 62 Of the Cataract. LVI. As then, Authors have not been fufficiently exad in their Det cription of this Adherence, between the Sclerotica and Choroides^ which is very neceflary for every Surgeon to know. I have found, by care- ful and repeated Diffedions, that this Adherence does not rife, from the Border of the Sclerotica^ round the Eye, at the Origin of the Cor- nea-Tranfparens ; but that, in the Middle, and lateral Parts of the Uvea^ there i^, a full Line, in Diftance, be- tween the anterior Border of the Sclerotica^ and the Ligame7ttum-Ci- Hare : And that here, the Adhe- rence is a full Line in Breadth ; when, on the Contrary, in the fuperior and inferior middle Parts of the Eye, it is jufl at the Border of the Scle^ rotica^ and not above ^ of a Line in Breadth. I have been the more exa<3: m, this Defcription, as it fo ef- fentially Of the Cataract. 6^ fentially concerns the Operation. See Plate I. and II. LVII. By this Account, it ap- pears, that all the Figures, g:ven of the Eye, have been faulty ; even that of Petu\ (8) the moft exad, is fo. For, by looking over fuch Figures, we fhould imagine the Iris to be quite ftraight ; and to arife immediately from the anterior Edge of the Sclerotica : But if we look into a human Eye, we will find that the Uvea does not anfwer to the Defcription, which the Plates give us of it. For it appears, in the Eye, to be of a convex Figure ; and juft adapted to the Parts contain ned within it ; and it's Convexity exactly to anfwer to the je ting- out of the Crjjlalin, Had Authors, but juft coniidered this Circumftance only, (8) Sa Letre, dans lequelle il demontre, que Je Cryftalin ell fort pres de I'Uvee, &c. 64 Of the CatArAci'. only, they would quickly have feeli the Abfurdity of even imagining, a Membrane to be formed here ; whe- ther from extravafated Matter, as St. Tvss imagines ; or from the Union of the more denfe Parts of the Aqueous-humour^ as the Antients fuppofed. This Circumftance Aque- ■pende?ite feemed well apprized of, where he declares, that it is impoC- lible to pafs the Needle, into the poftericr Chamber of the Eye, with- out wounding the Cryjlalm-Lem ; and this, long before it was imagin- ed, that the GataraSi was an Opa- city of the Cryfialtn. It is on this Account, that I have caufed three or four Cuts of the Eye, not, as it is generally reprefented, but as it really appears to be engraved, and joined to this Work. CoRROLARY. Hcncc it is mauifeft, that we fhould, not only fee, as well after the Operation, as we formerly did; Of the Cataract. 6$ did ; but alfo, that, the Eye has the fame Facility of altering it's Figure, according to the different Diftances of the Things regarded ; provided the Rays of Light have a free In- grefs to the Bottom of the Eye. LVIII. Since then, there is not any Danger to be apprehended from the Strudlure of the Parts ; and that thfeir Situation alfo favours the Ope- tion : General Evacuations, fuch as plentiful Bleedings, Purging and Bathing being premifed ; as aifo, a fpare, low Diet, for fome Days be- fore the Operation, to prevent In- flammation ; having chofe a clear ferene Day, it may be done thus : The Needle may be made of the fame Size, with the common Couch- ing-Needle ; with this Difference, that it fhould be quite flat, and edged, at it's Sides, as well as Point. The Eye lliould be pierced, about two Lines, and a Half, from the K Cor?iea^ 66 Of the Cataract. Cor?tea-'Tra?if parens^ in the ConjunC" ttva^ at the external Angle of the Eye ; for if you pafs the NeecQe, at Half a Line, or a Line's Diftance, from the Cornea^ as has been gene- rally dire died 5 you inevitably wound the Ligafne?2tum-Ciliare. It is alfo fafeft, to pafs the Needle in the Middle of the Globe, and not at all in the inferior Part of the Eye, as" is pradifed by fome ; becaufe, ty this Means, you chance to wound one of the principal Veflels, which compofes the V a fcular -Circle of the Eye ; they conftantly piercing the Sclerotica^ in two, or three different Places, in the fame Line, in the fu- perior and inferior middle Part of the Eye. It fliould enter horizon- tally, and pierce the Cryjlalin-Mem- brane^ towards it's pofterior Part ,- and continue the Separation of this Membrane, without in the leaft at- tempting to prefs on it's contained Body, Of the Cataract. 6j Body, which might be apt to flip out too foon. This Membrane, be- ing thus divided, you are then to deprefs both together under the J^i- treous-humour. It is to be obferved, that '3ifpeculum oculi here, far from expediting, rather hinders the Ope- ration, by prefling on the Eye, and fo, not giving fufficient Space for the Needle to move : 'Tis therefore, on this Account, juftly condemned by Heijler^ But, it may fometimes happen, that the Cryjialin may flip out, before the Diviflon of the Mem-^ brane is perfed:ed ; and in this Cafe, you pierce the Membrane in it's Center, fo as to divide it : And this you can the more eafily do, your Needle being in the Middle of it, and fo deprefs it, with the opacous Cryfialiii^ or turn it over, to the contrary Side of the Eye, to which the Needle entered ; and by this Means, your Operati9n will have the K 1 fame 68 Of the Cataract. fame Succefs, as if you precipitated both Le?2s and Membrane together. LIX. But I am fenfible, that fe- veral Objedions may be made to this Operation : Firft, from the At- taches of the Ligament tim-Ciliarey to this Membrane ; but I have evi- dently ihevi^ed, the Fahity of this Affertion at N. LIV, LV, LVI. It may alfo be objedled, that in divid- ing this Membrane, the Choroides may be vi^ounded in more than one or tw^o Places ; but as this Needle is edged, at it's Sides, thofe may continue the Separation of this Mem- brane, without in the'leaft affeding that Body. But, granting it w^ere wounded (which indeed may be fometimes the Cafe) need we be more apprehenfive of a Wound of this Part only, than when we find both it, and the Sclerotica wounded together, without the leaft Danger ? But then vou'll fav, the VitreouS" Tunick Of the Cataract. 69 'Tunick may be, by this Means, wounded, and of Confequence, this Humour loofened ; and Sight loft, as St. Yve^- (9) imagines. But it is to be noticed, that this is a pretty denfe Body, which eafily forms it- felf to the Part, which contains it : . Nor will pricking it, in feveral Pla- ces, make it change it's Situation ; which I have often tried, by placing it on my Hand. Nor is there any vifible Membrane to cover this Bo- dy ; for what furrounds it, is but a Sort of a Skin, which is nothing elfe but a Continuation of itfelf, in the fame Manner, as the White of an Egg forms a Sort of Covering, when expofed to the Air. LX. As for that Membrane, which covers the anterior Part of the Ft- treotiS' humour^ and furrounds the CryJialin-LenSy fo as firmly to fix this (9} Les maladies des yeux, chap. xx. 70 Of the Cataract. this Membrane in the Vitreous-foch et ; I imagine it to be, but, an Ex- panfion from the Procejfus-Ciliares ;' becaufe, beyond the pofterior Part of thofe Notches, you cannot poffi- bly feparate it. I have often endea- voured to continue the Separation further, by putting it into different Menjlruum s^ examining it, w^ithout any previous Preparations, ^c. but never could go any further. How- ever, it would be very advifable in/ the Operation, to avoid wounding> that Part of this Membrane, v^hich covers the Vitreous -Cavity^ than which, fure, nothing is ealier. LXI. Having then, I think, ma- nifeftly fhewn. That the Glaucoma and CataraSi are but different Narries, to exprefs the fame Diforder by : That the Reafon of the Unfuccefs- fulnefs of couching was not fuiEci- ently known ; and having fhewn the true Reafon of it, with a Method by Of the Cataract. 7 1 by which this Operation may be al- ways certain, &€, I fhall add, a Method of differing an Eye, by which, with one Eye only, you will fee all the Parts of this won- derful Organ, in jit u naturali ; and which cannot be done by the Me- thods recommended by fome (ij. LXII. With the Point of a Bit towry, or Lancet, you perforate the Corjtea-Tranfparens ; and then, by the Blade of a fine ScifTors introdu- ced, you entirely cut off this Part : And, as there is ftill fufHcient Space, between the Sclerotica^ and Liga- mentum-Ctliare^ you here apply a Forceps, by which Means, the Globe is not preffed, between the Fingers, nor any of it's Parts broke, or dif- placed. Then, with a fine Scalpel, you gently feparate the Ligament tum-Ciliare^ from it's Attaches to the (i*) Briggii opthalmographia, p. 73. CartelU Dioptric, cap, v, &c, 72 Of the Cataract. the Cornea-opaca^ quite round the Globe of the Eye. Then, by paf- iing one of the Blades of your Scif. Ibrs, between the Sclerotica and Choroides^ you divide this firft, and ftill continue with your Scalpel, to feparate any little Nerves or Arteries, which, by paffing from one to the other, might continue the Adhe- rence ; and by this Means, you fe- parate entirely the Sclerotica from the Choroides, LXIII. By this Means, you will fee all the Blood-VefTels, and Nerves, which are diftributed to the Iris ; The different Places, where they pierce the Sclerotica^ glide between it's Interftices, and enter into the Choroides ; particularly the two prin- cipal Branches, which compofe Ho^ vius's Arterial- circle, which fpread themfelves round the Iris, Thofe conftantly pierce the Eye, in two, or three different Places, in the fu- perior, Of the C ATAR ACT. 7 3 perior, and inferior middle Part of the Eye, in Men, as well as Brutes^ as numberlefs and indifpu- table Experiments have fatisfied me of. See Fig. i and 2. Then by continuing the Diviiion of the Cho^ roides^ in the fame Manner as that of the Sclerotica^ you will fee the Retina^ as alfo, with Care, the Ca- nal Godronnee of M. Petit ^ (2) the Cryjialin- Lens^ and Vitreous-hu- mour^ in their true Situation : The Capfula of the former ; which, not only exifts, but is alfo conliderably denfer, and firmer, than is gene- rally imagined. By piercing this Capfula^ you will fee Morgagnt^ Lymphatick Liquor iffue out ; and by preffing a little harder on this Body, the -Cryjlalin itfelf will flip thro' the Aperture. See Fig, 4. L LXIV. (2) Memoires de r Academic, 1726. 74 Of the Cataract. LXIV. The Iris^ or more pro- perly, the Choroides anterior^ is al- ways defcribed to be compofed of a double Row of mufcular Fibres : Thofe which immediately furround the Pupilla^ are orbicular ; and the radial ones are, on one Side, attach- ed to the orbicular Range of Fibres, and by the other, to the Ligame?i- tmn-Ciliare. The Ufe given to the Circular-fibres is, to contract the Pupil la ; and thofe of the radial ones, to dilate it. The celebrated Ruyfch (in Thefauf o^ ejus Anato- mica) tho' he defcribes the Iris after this Manner, yet he freely owns, that the Circular-fibres are not at all diftind ; and indeed juftly too : LXV. For, if you examine this Part with Care, you will find, but one Plan of Fibres, to wit, the Ra- dial ; for what gave rife to the Cir- cular-fibres, was, that the Part of • the Of the Cataract. 75 the /r/V, which immediately fur- rounds the Pupilla^ is thinner than the reft of this Body, and folded, as it were, in two or three Places, round the Circumference of this Fo^ ramen. But by carefully obferving, with a good Glafs, or even with the naked Eye, you will find thofe Fi- bres continue in ftraight Lines, thro' thofe Folds, from the Border of the Pupilla^ to the grand Circumference of the Iris» LXVI. But to put this Point en- tirely out of Difpute, it is to be noticed, that no Mufcle (the Heart excepted) can ad; without a punc- tu7n fixum. To prove which, no-« thing can be more evincing than the following Experiment. The anterior Mafloiden-Mufcles^ are, on one Side, attached to the Grove in the Mafloid-P rocejfus of the Os-Temparale ; and, on the L 2 other jS Of the Cataract. other Part, to the fuperior internal Part of the Clavicula^ and Top of the Sternum, Now the Ufe of thofe Mufcles is, to bend the Head forwards ; but this they only do in a horizontal Pofture ; becaufe, in an ere^t Pofture, the Plead naturally bends forwards by it's Gravity. But as the Sternum is not a iix'd Point, by reafon of the continual Elevation and Depreffion of the Ribs, the Re&i-abdominis^ which on one Part, are attached to the Sternum^ Car- tilago Rnftformts^ and two or three inferior true Ribs ; and by the other, to the fuperior Part of the Os-pubisj are alfo in Adion, at the fame time, to raife up the Head, in this Pof- ture. Without the Concurrence of which Mufcles, in order to make a pu?tBum immobile of the Sternum^ we could not, in this Situation, raife our Heads. After this Proof, even granting there were fuch Fibres, yet, I believe, no one w;ll fay, that they Of the Cataract, yy they could a<3: diiFerent from, or in- dependent of each other. LXVII. The Adion of this Part, may then, be thus accounted for^ The Pupilla^ in a State of Reft, is dilated : This is evident ; becaufe, whilft afleep, or in any State of In- adion, with refpedt to this Organ, we conftantly find it fo. When it contracts itfelf, the Eye becomes more oblong : The Cryjlalin and VttreouS'humour jet more forward, and fo, by this Mechanifm, we lengthen nigh Objeds. And the true Reafon, why we cannot fee dif- tindly, at a lefs Diftance than fix Inches, is, becaufe this Organ can- not form itfelf into an Eliptkal Fi- gure, fufficiently oblong, to catch their Focus. The Pupilla is dilated to view diftant Objeds ; by which the Eye becomes more flat, and it's Bottom nigher the Pupilla. This is, not fo much to let a greater Quantity 78 Of the Cataraci*;^ Quantity of the Rays of Light in at once, as to endeavour to gather the Points of thofe Rays, which come from the Objed we would endea- vour to view, to fall on the Bottom of the Eye, in order to be tranfmit- ted to the Se?ifGrium commune, LXVIII. But, becaufe Diverfities of Opinions are apt to puzzle Rea- ders ; and that I have feen the Sub- ftance of a Paper, read before the Royal Society (3), wherein the Au- thor endeavours to prove, that the Globe of the Eye, is conftantly the fame, on viewing all Objeds, at different Diftances ; and that even it was neceffary that the Eye fhould not change it's Figure, upon fuch Occafions ; becaufe, if it did, we could not judge of the Diftance, or Propinquity of Objeds. I own, the Thought to be very ingenuous ; and could (3) London Magazine, for July, 1 749. Of the Cataract. 79 could heartily wifh, that it were as true as curious. Bat as it is certain, that the Eye does change it's Fi- gure, which, I think, was never before called in Queftion ; and of Confequence, wanted not many Proofs. I muft therefore, to fup- port the Side of Juftice, fhew that it does. When we bring an Objed: infenfibly from the Diftance of good Sight, nearer the Eye, we obferve the Pupilla imperceptibly to grow fmaller ; and as the Image again re- cedes from it, to enlarge itfelf. Now neither of thofe Motions of the Pu- pilla can be done, without an Alte- ration in the Figure of the Eye ; therefore, when the Pupilla contrads itfelf, it does it by pulhng the Cho- roides anterior forwards ; which ne- ceffarily makes the Eye become more oblong. When the Pupilla dilates itfelf, it does it by making the Iris more fiat, and of Confequence, re- ceding from the Cornea^ and pref- fing 8o Of the Cataract. fing back the other Humours ; by which it is manifeft, that the Eye muft become more flat. Nor do thofe Alterations in the Figure of the Eye, in the leaft hinder the Diflinc- tion of the different Diftances of Objeds : Thus, for Inftance, when I hold an Objed: at about twelve In- ches from my Eye, I lee it dif- tin6i:ly ; yet as it gradually recedes from that Diftance, I ftill fee it ; but know, that it is at a greater Diflance, by the Pains which I take to obferve it, by my Eyes changing it's Figure. And tho' two Houfes, of the fame Magnitude, with ref-^ ped to each other ; and at a consi- derable Diftance, are feen by my Eye diftindly ; yet I know that one is nigher to me than the other, be-* caufe it makes a larger Angle on the Reti?ia. LXIX. How thofe Changes, in th^ Figure of the Eye are made, has Of the Cataract. 8r has been Matter of great Conteft. It has been generally believed, to he occafioned by the Ligamentt/m-C- /tare's advancing, or retradting the Cryftalijt ; but this cannot be, be- caufe the Cryjlali?! has no Adherence to this Part : Others have imagined it to be done, by Means of the Elon- gation and Retradion of the Chc'^ roides anterior ; but to this, there have been feveral Objedions made ; the moft weighty of w^hich is — - — If the Motions of the Choroides an- terior^ by Means of it's Attaches to the Ligamentum-Ciliarey were the Caufes of thofe Changes in the Fi- gure of the Eye, we could not fee Objects diftindly, but at two determi- ned Diftances ; that is to fay, in the States of Contraction and Relaxation of this Part. But fure this fame Objedion will hold good again ft thofe who affign the Changes of this Organ, to the different Adions of it's Mufcles, As for me, I believe M thofe 8 a Of the Cataract. thofe Changes are made by the Ch(h roides anterior ; becaufe the Pw pilla is always con traded, at the fame time, that the Eye becomes longer in it's Axis ; and when the Eye becomes more flat, the Pupilla is dilated. Now, if thefe Changes in the Eye were occafioned by the Power ot it's Mufcles only ; and of Confequence, that the Choroides an^ ter'ior were a Body purely paflive, it would neceflarily follow^ that whea the Eye would become more oblong, the Pupilla fhould be dilated ; be- caufe, being in itfelf without Mo- tion, it fhould give Room to the Body prefling on it : And for the fame Reafon, it fhould contract it- felf, upon the Eye's becoming' more flat ; becaufe it's Parts, by being flattened, or looflng of their Con- v^exity, fliould clofe each other. And as for the Action of a Mufcle, I be- lieve it has different Degrees of Con- traction : Thus, for Inftance, I caufe a ftrong Of the Cataract. 83 a ftrong Man to ftrip the Arm bare, and extend it : Upon his bending the Fore-arm, I perceive the Biceps (which, by one of it's Te7jdo77Sy is attached to the Coracoide Apophyfis of the Scapula \ and by the other, to the Grove in the fuperior Part of the Humerus ; and uniting, form one ftrong Tendon, which is fix'd in the Tuberofity, in the Neck of the Radius) to fwell: Upon caufing him to Hft up a large Book, I per- ceived it to grow much harder ; and upon railing up a Chair, I feel it prodigioufly hard and tenfe. By which it is manifeft, that the Power of A<^ion in a Mufcle, is in Propor- tion to the Refiftance of the Body ; and that the Contraction of the Pupilla^ is in Proportion to the Pro^ pinquity of the Objed regarded, LXX. As then, the Choroides a7t^ terior is a mufculous Part, which is conftantly in Motion, we fee how M 2 necefiary 84 Of the Cataract. neceffary it was, that it fhould be well fupplied with Blood -Veffels, and Nerves ; therefore Hovius\ Opir nion, that thofe Blood- Vefiels fup- ply the Humours of the Eye, with their Nouriifhment, cannot be true (4). I have very good Reafons to, think that the Aqueous-humour is fupplied by the Choroides fojierior ; becaufe, after you have difcharged the Aqueous- humour of the Eye, if you take out this Membrane, and put it into Water, it immediately tinges it, as t}ie Aqueous-humour would do. If you take it out of this, and put it into frefli Water, it gives it the fame Appearances ; and this it will continue to do, the' you repeat it feveral times : From which we fhould not be furprized at the Facility, v/hich this Humour has, upon being difcharged to recover it- felf again ; nor can I find any Dif- ficulty ,^ (4) pe circular! Jiiimorum mptu in oculis. Of the Cataract. 85 ficulty, in allowing, with Mery^ this Humour to be fecerned, by little glandular Points, placed in the Cho- roides pojlerior. LXXr. But this Affertion will ftill appear more evident, by an Ex- arnple which the celebrated Mery gives, in the Works of the Royal Academy y for 1707, of a Woman, who died at the Hotel Dieu oi Parisy who had a Glaucoma^ ftrongly ad- hering to the Irisy and which fhut up the Pupilla, After he had taken off the Cornea-tranfparensy there did not iffae out the leaft Drop of the Aqueous-humour : But when he had opened the other Coats of the Eye, pofteriorly, this Humour dit- charged itfelf abundantly. Hovius has fomething in relation to a Cata- radous-dog, in folio 85 of his Work, which fe^ms to confirm this Opinion. This Mery^ and who has been fo often before rnentioned, in this 86 Of the Cataract. this Work, feems, by all Accounts, to have been the fame, who was firft Sur- geon of U Hotel Dieu ; and whofe Criticifm upon Frere 'Jaques\ late- ral Operation for the Stone (5) ; and his other Works are held in fo much Efteem by the learned World. It is from this Piece, fome would pre- tend (6), that the famous Mr. Che- feldon borrowed his lateral Opera- tion, LXXII. At the internal Angle of the Eye, near the Caruncula-la- chrimalis^ is a femilunar Fold, de- fcribed only by the laborious Win- flow ; but I have found this Mem- brane, a Continuation of a Sub-, fiance, partly cartilaginous and bony, which reaches almoft to the Infer^f tion of the Optick-Nerve. From it's (5) Obfervations fur la maniere de tailler, dc Frere Jaques. (6) Parallele des differentes manieres de tir?r la piere, &c. fol. 133. Of the Cataract. 87 Jt*s Origin, where it forms this fe- milunar Fold, it infenfibly contracts itfelf, fo as to form a very narrow Neck, of a firmer Subftance ; from whence it again enlarges itfelf, fo as to form it's Body, or Belly, which as it augments in Bulk, encreafes alfo in Firmnefe 5 and becomes of a bony SubftancCj which terminates a little more pofteriorly than the In- fertion of the obliquus minor Muf- cle ; and exadlly between it, and the ReSius internus in an oval Form. This Subftance, which may be cal* led Os Opthalmicum^ or whatfoever other Name you think more expreC- live, forms internally (with refpeA to the Eye) a Concavity, which exadly anfwers to the Convexity of the Eye ; and feems wonderfully to facilitate the Motions of this Or- gan ; being in it's concave Part, li- ned by the Tunica-conjun&iva^ in which are here fituated, feveral lit- tle Glands, vifibie enough, thro^ which 88 Of the Cataract: which an oily fort of Subftailce ouzes out. It feems to me, to re- ceive fome flefliy Fibres, from the Interims reStus and Obliquus minor Mufcles ; and generally to anfwer to the Motions of the former. But as I can fay nothing of Certainty, with refped to it's Ufes, I fhall leave that to others : It is fufEcient for me, thus to have faithfully de- fcribed it. LXXIII. As I have made men- tion of HoviuSy in this little Trea- tife : I think it will not be amifs to give fome Account of his Work here ; more efpecially, as I fee fe- veral quote him, who were not tho- roughly acquainted with his Wri- tings. He had taken his Degrees at Utrecht in 1702 ; and took for his Dodorial Thefis, An circularis hu- fnorum motus in oculo ? This made a great Noife in the learned World, as well for the Newnefs, as the Sin- gularity Of the Cataract. %g gularity of the Difcovery : In 1 7 1 6, he publifhed it with large Amend- ments and Improvements, fiich as we now fee it. As for the Difpute between Ruyfch and him, on Account of it, I have nothing to fay, feeing, that he has pubUflied a* long Letter in his own Juftifi cation. It is certain, that his Difcovery of the Blood -Veflels in the Eye was very jufl: ; yet 1 cannot help finding Faiilt with him, for concealing the Means he made Ufe of, for this Difcovery : Howev^er^ the Method I have fuccefsfully ufed y and which is much more fure, and admits of lefs Difputes, than Injec- tions, how fine ibever, I have al- ready defcribed at N. L. and by the Help of fomething analogous to it, I have made more beautiful In- jedions in other Parts, than the moft penetrating and complex Mixtures could do. N LXXIV, 90 Of the Cataract. LXXIV. The Antients fuppofed, the Cryjlalin-Le?ts to be formed by a Sort of Tranfudation from the Vitreous-humour : the Aqueous-hu- mour the F(eces of the two former. Hovius thinks, that all tKe Humours of the Eye, are formed from the Blood-VefTels, which paffing over the Sclerotica^ are differently rami- fied thro' the Coats of the Eye. It was thofe VefTels, which Nuck imagi- ned, fupplied the Aqueous-humour of the Eye. {^Q^Plateh Fig. 2.) That Part which is fpread over the Choroides anterior^ he calls, duEius oculi aquo- fus. The Cryjlalin is a Texture of Nerves and Limphaticks^ Ad and AhduElor s^ arifing from the Liga- fnentum-Ciliare^ and croffing each other in different Manners ; and as it is entirely compofed of Lamince^ which feparate by Water, Hovius thinks, each Lamin has an Ab and AdduSor Veffel ; that is to fay, one Of the Cataract. 91 one which conveys it's Nourishment to it from the Blood, and that which returns it back again to the Heart. The Fitreous- humour re- ceives it's Nourishment from the fame Fountain ; with this Diffe- rence, that thefe Veffels pafs off in ftraight Lines, entering it at one Part, and leaving it at the other Extremity. Thofe Veffels rife chiefly from the Ligamentum-Ciliare ; and others of them, from the little Ra- mifications of Blood-Veffels fpread over the Choroides, LXXV. As then each of thefe Humours has an AdduSior Veflel, or one that brings it's Nourifhment from the Heart ; and an AbduSioVy or one that returns back, this Liquor again, it may be eafily feen, that there is a continual Regeneration, and Circulation of the Humours in theEyg. That is, that in ^vtvy Syjiole of the Heart, the Blood is thrown into N 2 the gi Of the Cataract. the Veffels of the Eye, and by them equally expanded thro' all it's Parts y and in every Diaftok fent back by the Veins. Now, let us fuppofe a Dog, the Quantity of whofe Blood to be a Pound ; and granting, that no more than Half a Grain were thrown into the Eye, at every Con- tradion of the Heart. As the Heart has above two thoufand Pul^ fations in an Hour, as Harvey^ Da circulatione Sanguinis ^ obferves ; and which Lcwerus fays, is the leaft. Now it is manifeft, that in an Hour's Time^ there cannot be lefs than one thoufand Grains, or two Ounces, two Scruples ; which in twelve Elours, is a Pound, nine Ounces ; and confequently, in both Eyes, there is three Pounds, two Ounces, in that Space of Time. But that this Circulation might be more evi- dent, I made an Aperture into the Cornea^ and after the Aqueous rhu^ tnour Oj the Cataract. 93 ffiour had difcharged itfelf, I applied a Bottle to the Part ; and befides, three or four Drops that were loft, there fell into the Bottle, twenty- three Grains, in twelve Moments time. Now, fuppofijig a like Quantity to be fecerned, for the CryJialin-LenSy in the fame time, and four times that Quantity for the Vitreous-humour^ we fhall find, in twelve Moments time, 156 Drops, or two Drams, one Scruple and fixteen Grains of Humours in each Eye. Now for a more evident Proof: If you tie they/i{g'^/^r-/^^/;^,the Rye immediately fwells, becaufe the Humours, which fhould be turned back, from the Eye, are here obr ftrudted. But if you tie the Caro^ tid-^Artery^ the Eye immediately becomes flaccid, and dull ; becaufe the Humours are hindered a PafTage to it, From all which Experiments, it is evident, that there is a con- stant Circulation of the Hu-s M0UH5 ^4 Of the Cataract, MouRs IN THE Eye. — -- Thus far Hovius* LXXVI. But granting, (as it cer- tainly is) that the Blood- Veffels of the Eye have this conflant Circula- tion, can we from thence infer, that the Humours have the fame ? As the Origin of them is, that Trunk, which feparates into two or three ^Branches, at the pofterior Part of the Sclerotica^ by what Mechanifm can it's Expaniions feparate Hu^ mours fo different from each other ? The minuteft Canals, or Extremities of Arteries, feparate the Ljmphy yet thofe are Liquors, quite different from Lymph ^ and yet imagined to arife from and go to the Blood. It is certain, that the Blood fecerns Liquors different from itfelf ; as for Inftance, the Bladder^ UrinCy the Liver ^ Bile^ &c. But then it muft be alfo granted, that thefe Secretions cannot be made, without th^ Interpofition of fome glandular Of the Cataract. 9 ^ glandular Subftance, fuch as the Lh^ ver^ Kidneys^ &c. But, with ref- ped to the Eye, there are no fuch Subftances, to fecem thcfe Humours from the Blood. LXXVII. But to come clofer to the Point : By this Experiment on the Dog, he would prove the Con- ftancy of this Circulation, and Fa- cility of the Regeneration of the Humours of the Eye, by fhewing, that in twelve Moments Time, more Blood is thrown into the Eye, than all the(e Humours, put together, can weigh. But if a determined Quan- tity of Blood is thrown into the Eye, at every Contraction of the Heart ; confequently the fame Quantity is returned back, at each Dilation of this Part. If then the Aqueous-hu^ mour be difcharged, the Blood can- not be fuppofed to give lb imme- diate a Repletion to this Part, with- out lefTening the Quantity to the other 96 Of the CATAftAcf i other Parts ; feeing that in an Hour's Time, the Aqueous-humour is again regenerated, as frequent Experiments prove. But the Reafon why this Humour is fo immediately formed, and why the Iris is fo well ftored with Blood- Veflels, I have already fhewn at N. LXX. LXXVIII. Bat this imaginary Cir-- culation will be found ftill more weak, by the Remarks of Petit the Phyfician (7) ; who fhews, that the Cryjialin-Lens has no Communica- tion with the adjacent Parts, either by Blood- Veflels, or other wife. Bat to prove that the other Humours, have not this Facility of Regenera- tion, the Procefs of couching evi- dently fhews ; and I find nothing more pertinent to this Subjed, than what the late learned Dr. Molyneaux^ of Diibliny relates, in an elegant Latin (7) Memoires tie I'Academie, 1730^ Of the C AT AR ACT. 97 Latin Memoir ^ given into the Royal Society^ and printed in their Works, for 1730 (8). He tells of a Sol- dier of Ktlmatnhim^ whofe Lyes being catara&ous^ were both couch- ed : In about nine Years after, the Man died of an Inflammatory ^Fever. Upon examining his Eyes, there was not found the lead Remains of a Cryjialin : From hence, he thinks, (as I do alfo) that after couching, the Cryjialin infenlibly waftes away, fo as in Time, not to leave the leaft Mark of it behind. If then. Dr. Hew\ Opinion were true ; it would confequently follow, that a new Cry Jl aim fhould be formed, in about an Hour's time, after de- preiling the former, LXXIX. Butbyhislnftancesofthe Ligatures of the Jugular-Vein and O Carotid-^ (8) Philofophical Tranfaftions, N. 3 84. p, H9- 9? Of the Cataract. Carotid" Artery^ he feems to make it unqueftionable ; but if you will eonlider the follov/ing Remarks, yoa will find that thofe Experi^ merits prove nothing for him : it is certain, that if you tie the Ju- gular-Vein, the Blood. Veffels of the Eye will be diftended, becaufe they cannot return their Contents to the Heart. It is equally true, that in tying up the Carotid- Artery^ the Eye lofes it's Brifknefs ; yet it is al- fo as fad:, that in both Experiments the Humours of the Eye, are, nei- ther augmented, nor diminifhed in their Quantity. From hence then, it is manifeft. That there is not ANY Circulation of the Hu- mours IN THE Eye. LXXX. Lewenhoeck fays (9), that the CryJ}ali7t-Lens is compofed of exceeding fine Threads, or Fibres, croffing (9) Philofophical Tranfaflions, N. 293. Of the Cataract. 99 crofling each other differently, and clofely connected together ; without which, it were impoffible for this Body to keep it's Tranfparency : Hovius feems to have borrowed his Defcription of it from him. But this Body itfelf may probably be formed, by this L^ymphatick Liquor brought to it, by the Canal of the Cryjlalin-Capfula ; and it's diffe- rent Degrees of Conliftence, accor- ding to the different Ages of the Ani- mal ; all which the learned Petit has elegantly defer ibed (i), feems to make it more than barely probable. LXXXI. The black Subfiance, with which the Choroides poJlerioT is lined ; and which I believe, with Mery^ to be the Origin of the Aqueous-humour^ M. L,e Cat ( 2 ) very humouroufly accounts for, by O 2 fuppofing (•i) Memoires de r Academic, 1726. (2) Traite des Sens, p- 378. 100 Of the Cat ATLAcr. fuppofing, that the Sulphurs of the Blood, being here, intimately mixt with the Succus Ner^vorum^ which he imagines has fome Analogy to ^luick-Jilver^ forms this Blacknefs ; Or, Mercury^ joined to Sulphur^ forms a black Powder. LXXXII. Had M. Le Cat exa- mined human Eyes, as well as thofe of Brutes, he would have found the Choj^oides lined with a darkifh Browny inftead of a black Subftance. For, whatfoever be the Colour of the Cho- roides^ fo will that of the Aqueous- humour be ; and therefore, it is black in Sheep and Calves, &'c, and of a clear Brown in Men and Dogs, ^c, Howfcever, this we may explain, according to his Hypothecs ^ by -up- poiing the Eye to abound more with Sulphurs than Mercury ; and therefore there is not fufFicient of the latter, to blacken the Choroides : and this perhaps might be the Rea- fon, Of the Cataract, ioi fbn, that Sheep's Eyes are more fprightly than human ones. Such odd Notions it is, that makes fo many voluminous Authors in Phy- fickj and fo Kttle to the Purpofe. ^ LXXXIII. By often confidering how fufceptible the Eye is to violent Inflammation, after precipitating the CataraSi^ and frequent Experiments on that Subjed ; I think, I have found out the true Reafon of it, which no one has yet attempted ; and which is of too interiftinor a Nature to be here omitted. The opaque Cryftalm^ after the Opera- tion is generally placed, in the an- terior and inferior Part of the Eye, between the Proceffus-Ctliares and Vitreoiis-humour, By this Means, the Artery of the /r/V, < already def- cribed, (N. LXIIlj is comprefs'd : In Confequence of the Compreflion here, there is too great a Dilatation of 102 Of the Cataract. of the Parts elfewhere. TheVeffels on the Chorotdes pojlerior (which I believe, with Mariotte (3) to be the immediate Organ of Vifion) are fil- led and diftended : On this Account, the Rays of Light ftrike with too great an Impetus ; Or, the weakeft Light, at this Time, gives too fen- iible a Vibration to thofe Parts, al- ready too much ftretched. From this then the Pain, Inflammation, weeping of the Eye, &c. may be reafonably accounted for. This al- fo, juftly, explains, why the opaque Body, fometimes rifes again, in con- fequence of this Inflammation. From all this, then, it will appear, how necefiTary it is, to make plentiful Evacuations, antecedent to the Ope- ration, as already direded (N. LVIII.) It was for Want of thofe previous Preparations, that fo few amongfl: the (3) Ces nouvelles decouvertes, touchant la vue. Of the CArrhVikcT. 103 the Number of Poor, which the German Ocuiift lii timer ^ operated on, laft Winter, in London^ reco- vered their Sight. His Method was, any one who offered themfelves to him, he immediately operated on, by ftriking his Needle into the Eye, as fome are wont to do, in perform-? ing the Operation of the Paraccn- tejis. By this Means, the Needle ufed to enter, fometimes at the Borr. der of the Sclerotica ; at other Times, two or three Lines more porter iorly. But, befides this inde- cent Manner of operating, his Nee- dle was very injudicioufly contrived ; being juft the Make and Size of a large Stocking-needle : By this Means, very often, after the Needle was paffed into the Eye, the Opa- city remained ; fo that I have feen him, after turning his Needle back- wards and forwards, in the Eye, for above fix Moments, obliged to draw it out again, and the Opacity re- main 104 Of the Cataract. main behind. His Antagonift Taylor certainly knew more of the Eye, and was an excellent Operator ; but Hilbner had two Advantages over him : One, in being a Foreigner ; the other, in not fpeaking Englijh, The only Application he made \J{q of, after the Operation, was, to moiften a Comprefs in a Mixture of the Whites of Eggs and Sugar of Lead^ and fo apply it to the ope^ rated Eye, and let Nature do the reft. LXXXIV. Taylor always made Preparations, by Phlebotomy^ pur- ging^ &c. previous to the Opera- tion. The Needle he ufed was Piano-Convex, It's convex Part was marked by a black Line in the Handle. But if Hillmer made little Ceremony in performing the Opera- tion, this was as much on the other Extreme ; infomuch that he would b^ Half an Hour tying and untying his Of the Cataract. 105: his Garters, turning and winding his Ruffles, and accommodating him- felf for this grand Affair. But, be^ caufe he pretended to have mighty- Advantages by his Method of ope^ rating, I fhall relate it at full Length, fuch as I have heard him defcribe, and feen him perform, above thirty Times. LXXXV. General Evacuations being ufed, and the Day jfixt for the Operation ; after the Patient had been feated, and expofed to a pro- per Light, and the Dodor had alfo fixt himfelf : The Eye-lids being feparated from each other, he fixt his Speculum Oculi^ by which Means, the Eye was kept firm, and expofed for the Operation. He then, taking his Needle, with it's flat Part, next the Eye, and it's convex Part exter- nally, pierces the Eye with it, ex-- adly in this Pofition. The Needle P enters I o6 Oj the . Catarac'j'. enters the Eye^ in it's inferior and lateral Part, towards the external Angle : He then gently elevates the Handle of the Inftrument, inlarges the Aperture of the Cryjialin-Cap- ftda^ in it's inferior Part, and thus precipitates the opaque Body. The Operation being oyer, the Eye is immediately clofed, by a Comprefs dipt in Spirits of Wine, and 5i, the Patient bled in x\i^ Jugutarj and ordered a Purge for the next? Day. 7rr{ ^Ai it^liii i noil ia'^q^j "^uiiJi '. ' ^- h-JiOazo bn.n b^jj^ol i\\yA -LXXXVI,4'he> great Advanta^ ges, which xhcrDo^or promifed hint-^ felf by this Operation, were ; Jirjf^ by this Means, he pretended to avoid wounding the Ctliar^-Ner'ues'y^ and of Co^fequence, very little o3f Pain or Inflammationy we;re to bcf appreiien^d from the Operation t Seco?idlyj~'\^-Qte, the Cryjialin in a (olid, or fluid State, it always occu- pied Of the Cataract. 107 pied the anterior and inferior Part of the Eye, fo that there was never any Fear of it's mixing with the other Humours, and of Confequencc, of offufcating them. As for the Operation defcribed on his Book (4) tho' he fpends Time and Paper enough in fbewing it, yet it is fo confufed, and at the fame time, fliews fo Httle Knowledge of the real Situation of the Cryjialin^ and it's Attaches, that I have riot thought fit once to mention it. LXXXVir. But the Danger that is to be apprehended from this Ope- ration, is more than an Equivalent for it's Advantages. Firji^ from the Danger of wounding the infe- rior Artery of the Rye^ from which Accident, the entire Lofs of Sight P 2 is (4) Le mechanifme du globe de Toeil, p. 141, ^ 167, io8 Of the Cataract. is very much to be feared. And as to the Ciliary^ Nerves y they enter into the Ligamentum-Ciliare at all Sides ; fo that it is impolTible to ^void wounding them, whatfoever Way you operate. It is true, yoS very readily difcharge the impac-^ ted Body by this Operation; but it is aifo as certain, tha.t you will as readily and effectually do it in the Way I have defcribed, even tho' you have not a Mind to take away the Capfula, And as for the Spe-- culum Oculi^ I have already obferved the Difadvantages of it, atN. LVIII. As for Hillmer\ Method, it is cer-r tainly very bad. For the Needle, which is fmall, piercing the Capfula^ depreifes the CryflaUn^ rather by di- lacerating the Membrane, than any thing elfe. By this Means, alfo, the Q'-yflalifi is broke, and Part of it puQied into the Aqueous-Chamber pf the Eye. In a V^ord, then, it {hews Of the CkrAVikcT. 109 fliews fo little of the real Know- ledge of the Structure of this Part, and of the Body itfelf, which Ihould be taken away : Not to mention, that two Eyes are never wounded in the fame Place ; becaufe, in- ftead of gently piercing the Coats of the Eye, he immediately ftrikes his Needle into them, that it needs no Words to condemn it en- tirely. LXXXVIir. The Needle ufed by St. Tves (j) is flat and edged ; and with it he pierces the Sclerotica^ at a Half, or at moft, a Line's Dit tance, from the Cornea-Tranfparens : But by this Means, not only the Lu gamentum-Ciltare is wounded ; but alfo the ProceJfuS'CiliareSy which he would endeavour to avoid, are cer- tainly touched, by the Dired:ions which (5) Les maladies des yeux, chap, xx. no Of the Cataract. which he gives. Heijier\ Needle (6) is Piano-Convex^ and with it, he pierces the Eye, at about two Lines diftance from the Cornea : The lame Method is ufed by Briffeau, Petit the Phyfician (7) perforates the Eye, at about two Lines and a Half from the Corjiea^ as 1 have di- redled. But he alfo owns, that the Cryftaltn-Capfula has an Adherence to the Ligamentum-Ciliare : And this Aflertion the morefurprizedme, fee- ing that he took upon him particularly to defcribe the true Situation of the CryJialin-LenSy and this Body, in anfwer to fome Remarks on the Ca^ taraB^ given by M. Hecquet^ in his Trait e des Amares (8). Profeffor Ferren\ (6) Traa. de Catara(aa, p. 298. Trad, gus Chirurg. (7) Memoires de I'Academie, 1726. (8) Sa letre, ou il demontre, que la Cryfta- lin, &c. Letre des reflexions, &c. Of the Cat ARAcr. iii Firren\ Diredions for this Opera-- tion are pretty nigh the fame with Petite, LXXXIX. I think I cannot con- clude this Work, without making fome Remarks on the Operation of an imperforated Iris^ or Artijicial Pupilla^ as defcribed in the Work* of the Royal Society (9) ; and from, thence, by* Mr; Sharpy in his Sur- gery, feeing that the Spbjec^ I haver treate;d on^ xequires I jQiould take Notice of it. • Iithink th^n, that the Operation fe l^y ^offible to/ \^ done,; but .^tj^at any Benefit fhould aecrue fi*pni,.it, I think to be abfor. lately impojjible \ and that for the following Reafons. Firji^ it is im- poffible, to p^fs the Iris Needle, between .tlie Cryjialin-Lens^ and: Uvea^ without wounding the for- mer : (9) PhJlofophical Tranfa(^i9Jas, for ly^^ 112 0/ ^^^ Cataract, mer : If then there is Httle or n6 Space between them in the natural State of the Eye, there muft be ftill lefs, when this Part is comprefs'd hySiSpecukim oculi^ which by the Au- thor is deemed abfolutely neceflary vet this Operation. Secondly^ if the Cryf- talm-Lens be wounded, an Opacity will be neceflarily formed in Confe- quence of the Solution of Conti- nuity in this Body. Of this I faw a remarkable Inflance in a Shoemaker's.^ Boy in London ^ this laft Winter, who Tiad wounded the Cryjlaliny hf an Awl's piercing the Cornea ; and? which Opacity Dr. T^^/^r removed in Exeter "Change in about ten Day* after. -^ XC. But left I fhould feem to prejudice the World againft this Method, or leffen the Weight of the celebrated Author's Account of Z^/- Jion^ 6cc. in that Memoir^ Truth obliges Of the Cataract. 115 obliges me to declare, that the Pa- tient might fee immediately after the Operation, and fo far his Ac- counts were certainly true ; becaufe, tho' the Cryjlalt7t were wounded, yet the Parts would keep their Tran- fparency for fome time, by Means of this Lymph^ which fiarrounds the Cryflalin ; . as for Inftance, an Hour or two ; yet ftill, that the Patient fhould reap any further Ad- vantages by it, is, what I abfolutely deny. Howfoever, his imagining fuch an Operation, which the fup- pofed Situation of thofe Parts, feem^ ed to countenance, (there being al- ways fuppofed to be a confiderable Space, between the Chorotdes ante-' rior and Cryjialin-Lens^ which was filled up with the Aqueous-humour ) deferves Applaufe. XCI. If then, at any time, this Operation, (which may properly Q^ enough 114 Of the Cataract. enough be called Koreotomy (i), feeing that we are fo fond of Greek Terms) may fucceed, it feems to' bid faireft for it, when done thus. The Patient being prepared by Ve- nefeEiion^ 8cc. he fhould feat himfelf before a good Light, in the fame Manner, as if for couching. Then the Surgeon fhould apply the Spe^ culuin Ociili^ to fix the Eye firm ; and with a CataraB^ or Iris Needle, perforate the Cornea-Tranfpare?ts^ in it's inferior Part. The Needle fhould enter obliquely ; and when you per- ceive it has entered thro' this Coat, you fhould lefTen the PreiTare of the Speculum^ without entirely remo- ving it ; and then gently perforate the Iris in it's Center, and then draw out your Needle, and remove the Speculum Oculi, The Eye fhould be clofed, and every other Circum- ftance h) Jko^ Pupilla^ et rlii^fu fecare. Of the Cataract. 115 fiance obferved, as if for depreffincr a CataraSi : And by this Method only, you may perform fuch an Ope- ration, without wounding the Crjf- falm-Lem. j4n Figure PLATE :i ^T li ' An EXPLANATION oj Plate the I. Fig. i. and 2. Figure the ift. H. The Cornea-Tranfparens , 2- That Space between the Cor- nea and Choroides anterior^ com- monly called the a^iterior Chamber of the j4queouS'hu7nour, X a. The Uveay IriSy or Choroides anterior, ^. The CrjJlalin^LenSy as it ap- pears, on taking off the Cornea. n. The Ligament um-Cili are, K The Sclerotica^ being the firft of the three Membranes, in which the Humours of the Eye are con- tained. T. The principal Trunk, from which the Eye receives it's Blood- Veffels ; taken from Hovius, n. The Optick'Nerve, o. An Artery,, which, twining round the Optick-Nerve^ pierces it, and fo ramifies itfelf on the Retina and Vitreous-humour, Figure Figure the 2d. 1. The Choroides aiiterior, D. The Cryjlalin-Lens, h. The Arterial Circle of the Cho- roides anterior : The fingle Strokes, afcending and defcending from it, Ihew the Ramifications of lefler Vef- fels proceeding from it. D. The anterior Border of tlie Sclerotica^ where the Cornea-Tra7tf' parens hegins, rifing; more anteriorly than the Choroides anterior : The Space between it, and the Iris, fhews the Diftance there is between the Be- ginning of the Sclerotica, and Li^a- fnentum-Ciliare, X The Sclerotica, 0. The Of tick-Nerve, An K Figure the 2d, \ The Choroides anterior. 3. The Cryjlalin-Lens, V. The Arterial Circle of the Cho- roides a7tterior : The fingle Strokes, afcending and dcfcending from it, Ihew the Ramifications of lefler Vef- fels proceeding from it. D. The anterior Border of the Sclerotica^ where the Cornea-Tranf- parens begins, rifino; more anteriorly than the Choroides anterior : The Space between it, and the Iris^ fhews the Diftance there is between the Be- ginning of the Sclerotica^ and Liga^ mentum-Ciliare, a. The Sclerotica, 0. The Opttck-Nerve^ An An EXPLANATION of Plate the 11. Fig. 3, 4, and 5. Figure the 3d. A. The Pupilla, B. B. The ir/>j or Choroides aU" terior* C. C. The Vafcular -circle of the Iris : The three Threads, which enter into the Ligamentum^Ciliarej and form this Circle, are the DuBus Aqtioft of Nuck^ and which pafs from the Sclerotica to the Choroides^ exadly as marked here. D. D. The Ligament um-Ciliarey truly delineated. E. E. are little Blood-Fejfels^ and Nerves^ which are dilperfed round the Liigamentum-Ciliare^ and arifing chiefly from the Sclerotica, F. The Choroides pojierior, G. Fart of the Retina, Figure Figure tha 5th, *. The juft Figure of the diffe- rent Ramifications of a Blocd-Vejfel^ which fpread itfelf over the poftcrior Part of the Cryjlaliji-Capfula, See N. XLIX. Figure the 4th. H. The CryfiaUn-hens^ contain- ed in it's Capful a^ and lodged in the Cavity of the VureouS'hu7nour^ to which it is fix'd by the Continua- tion of it's Membrane^ having it's Rife from the Litgamentiaft^Ciliare^ L The Vitreous-humoiir. K. The Coronce-CiliareSj or In- dentations of the ProcejJuS'Ciliares , L. The Diftribution of a Blood- Vej^el^ on the Vitreous-humour. FINIS. % & % ^^