I R I 



pavilion, there are gardens belonging to the principal inha- 

 bitants of loannina, moil of whom have fummer-houfes. 

 The population is variouny ilated : fome compute the 

 number of houfes at 8000, and others cftimate tlie number 

 of inhabitants at no more than 35,000. From the commer- 

 cial tranfadtions of this city, the vizier draws a revenue of 

 250,000 piaftres. Hobhoufe's Journey through Albania, &c. 



lODATES, Iodic Jc'uI, Iodide, in Chemijlry. See 

 Simple Bodies. 



IODINE. This newly difcovered elementary fubftance 

 lias been correctly defcribed under Simple Bodies, to 

 which, therefore, we refer our readers. 



JOHN of Gaunt, 1. 2, for third r. fourth. 



JOHN BAPTISTE, in Geography, a parifli of German 

 Coail county, in the territory of Orleans, containing 2990 

 inhabitants. 



JOHNSBURY, St., 1. 3, ,-. 1330. 



JOHNSON, 1. 2, r. 4867 ; 1. 3, r. 2330. Add— Alfo, 

 a town of Franklin county, in Vermont, having 494 inha- 

 bitants. 



JOHNSTON, 1. 3, r. 1516. Dtle the laft pai-agraph, 

 and infert — See Joiixsox. 



lOLITE. See Mineralogy, Addenda. 



JONES, 1. 3, ;•. 4968 inhabitants, of whom 2375 were 

 flaves in 18 10. — Alfo, a county of Georgia, which, with its 

 town Clinton, contains 8597 inhabitants ; the number of 

 flaves belonging to the county being 2574, and to the town 

 63, in 1810. 



" JONESBOROUGH. Add— a townihip of Wafliington 

 county, in Maine, having 553 inhabitants. 



JOSEF, St., 1. 16, r. Tucuman. 



IPECACUANHA, 1. 33, add— The plant is now 

 known to be the Callicocca. 



Ipecacuaxha, Chemical Properties of. See Emetin. 



IPSWICH, 1. 6. — In the year i8n, by the parlia- 

 mentary returns, it contained 2732 houfes, and 13,670 

 perfons. 



IRA, a town of Rutland county, in Vermont, having 

 519 inhabitants. 



IRAC, 1. 17, after wine, add — This province is divided 

 into five great diftritls, and each of thefe into hallooks, or 

 lelTer d"iftricl;s. The five dillrifts are, Ifpahan, Tehraun, 

 Naen, MuUagar, and Kermanfliaw, See each. At the clofe, 

 add — See Yezd, Kom, Tehraux, &c. 



IRAVAT, 1. 15, for thunder, bearer r. thunder-hearer. 



IREBY. In 181 1, the parifh, comprehending High and 

 Low Ireby, contained in the former townfhip 26 houfes, and 

 130 perfons, i;/z. 62 males, and 68 females; and in the 

 latter, 41 houfes, and 269 perfons, wa. 137 males, and 132 

 females. 



IRIDIUM. See Mineralogy, Addenda. 



IRITIS, or Inflammation of the Iris. ProfefTor Schmidt, 

 of Vienna, firil accurately difcriminated this difeafe from 

 other kinds of ophthalmia, and applied to it the foregoing 

 name. The iris often becomes inflamed in confequence of 

 artificial or accidental woundsof the eye-ball. Conftitutional 

 fyphilis frequently affefts the eye, producing a peculiar and 

 charafteriftic iritis. The iris is the texture, which is the 

 feat of inflammation in the diftinft kind of ophthalmia fo 

 frequently met with in gouty conftitutions. In the rheu- 

 matic ophthalmia, the inflammation, though never originating 

 in the iris, frequently extends to it. And, laftly, an inflam- 

 mation of this membrane fometimes accompanies cutaneous 

 eruptions ; particularly thofe wliich, though not fyphilitic, 

 have fucceeded fores of the genitals, and are generally fup- 

 pofed to be connefted with the abufe of mercury. 



I. In common inflammation of the iris, or idiopathic iritis, 

 Vol. XXXIX. 



I R I 



befides the common fymptoms of ophthalmia, there are 

 changes which occur at the very commencement that indi- 

 cate the feat of the niflammation. The pupil is contracted, 

 the motions of the ir.s are lefs free, and the pupillary open- 

 ing lofes the bright black colour which it naturally pofTelTes. 

 Ihe colour of the iris is next obferved to alter • this hap- 

 pens hrll ,n the lefll-r circle, which gets of a darker hue ; 

 and afterwards in the greater, which grows green if it has 

 been greyiih or blue, and reddift if it has been brown or 

 black. The ins afterwards fwells and projects towards the 

 cornea ; and the margin of the pupil lofes its Iharplv defined 

 edge, and is turned back towards the pofterior chamber, 

 ihe rednefs accompanying thefe changes is by no means 

 confiderable, and is at firil confined to the fclerotic co.it, 

 in which a number of very minute rofe -coloured vcfTels 

 are feen running in ilraight lines towards the cornea. The 

 pupil, at the fame time, lofes its circular form, becomes 

 iomewhat irregular, and prefents a greyilb appearance. 

 Examined with a magnifying glafs, this appearance is feen 

 to be produced by a fubftance very like a cobweb, occu- 

 pying the pupil, and which is foon afterwards diftinguilhcd 

 to coniiil of a delicate flake of coagulable lymph. Into this, 

 the proceffes or dentations of the margin of the pupil feem 

 to flioot, and it is afterwards found, that at thefe points ad- 

 hefions are apt to be eilabliflied, in confequence of which 

 vihon IS rendered more indiilintt, and only one fide or parts 

 of objefts can be difcerned. 



The cfFufion of lymph into the pupil continues to in- 

 creafe ; it is likewife poured into the pofl;erior chamber, and 

 adhefions between tlie iris and capfule of the lens are formed. 

 The quantity of lymph effufed is fometimes fo great, as to 

 fall in a curdled form from the pupil to the lower part of 

 the anterior chamber. The pupil, the fize of which is con- 

 hderably diminilhed, now derives a greyifh-white colour from 

 that of the lymph by which it is filled; the morbid fenfi- 

 bility to light, which prevailed at the commencement of the 

 inflammation, is diminilhed ; the powers of vifion become 

 gradually more and more limited ; and, at length, merely the 

 perception of light remains. 



By this time, the rednefs of the eye has increafed, and 

 partly arifes from vefl!els which are now developed in the con- 

 junftiva. The rednefs is deepell all around the cornea ; 

 towards the periphery of the eye-ball it fades. The cornea 

 lofes fomewhat of its peculiar brilliancy ; and lymph now 

 appears to be eftufed into tlie fubftance of the iris ; for, 

 while it projefts more and more towards the cornea, its 

 fibres are coUecled into bundles, and its furface exhibits a 

 puckered or plaited appearance. A yellowifli-red tubercle 

 then forms on fome part of its furface ; it is at firft fmall, but 

 enlarges and projeds forwards, and, according to Schmidt, 

 is diftinftly feen to be an abfcefs, which finally burfts, and 

 difchargcs its contents into the anterior chamber. At this 

 period of the difeafe, a fmall quantity of blood is fometimes 

 extravafated into tlie anterior chamber. The inflamma- 

 tory fymptoms now abate, and, as the difeafe fubfides, both 

 the pus and blood in the anterior chamber are ablorbed. 

 The (hreds of the cyft of the abfcefs, which were floating 

 in the aqueous humour, in a few days difappear. The an- 

 terior chamber regains its tranfparency ; the iris remains 

 permanently expanded ; its puckered appearance continues, 

 the pupil is clofed, and the power of vifion is entirely loft. 

 When the termination is fomewhat more favourable, the 

 pupil is not entirely clofed, and the iris retains fome degree 

 of motion. The piece of ccigulable lymph which occu- 

 pies the pupil is reduced to tlie ilate of a thin membrane, 

 which is opaque towards its centre, but fomewhat tranf- 

 parent at the edges ; tlie marpnn of the iris is only adherent 

 3 U at 



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