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I HE last subdivision of the classification includes iboso classes of remedies, the operatiou of whicli is mei ely mecha nicat. Under this I have placed Diluenis, Demulcenis, In mollienis, and A thelmintilas. They are classes of comp ratively litile importanCe. CI P. XX. OF DILUENTS.D1LugsTs have been defined, Substances whicli increme the fluidity of the blood, by augmenting the proportion os fluid in it. Watery liquora, it is obvious, will have this operationto a certain extent, Ud, Strictly Speiniura water is the onlyproper diluent. But different mild substances are added tolt to render it pleasant, and frequently to communicate in ita demulcent quality, diluenis and demulceuis heing generallyemployed to auswer the sanae iudications. With the formor intention water is infused on scorched bread ; or a decoctionos bran is used. Gruel, whicli is a decoction of tho gratias of the oat, Deed si ona thoii' luish, is the most common lubri-
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DEMULcENTs are defined, - Medicines suiled to obviatoand prevent the actiori of acrid and stimulant matters ; and that, not by correcting or changing their acrimony, but byiuvolcing it in a mild and viscid mattei', whicli prevenis itfrona actuag upon the sensibie paris of the body,V 0r bycovering the Sursace to which they may be applied. Theid action has been supposed to be exemplisied in catarrh, wheretho irritation at the top of the trachea, occaSiOning coughing, is removed by mucilaginous SubStances ; OP in gonori licea, ere the sense of heat and pain frona the application of the stimulus of urine to the inflamed sursace of the urethra isprevented by similar meanS. Where these substances are directly applied to the pari, it may be understood how this operation is obtained froni them. But where they are received by the medium of the stomachinto the circulating system, it has been supposed that th can have no sucti esse l. They must be changed by the prο-
ess of digestion, and lose that viscidity by whicli only theyoperate, so that they cannot afterwards be separated by any secretion in their original forni. Hence their utility in gonori licea and simitur assections has beon altogother dentia. It is not cloar, howover, that such a concluSion is just. Iitis sufficiently certain, that many substances, Whicli underio the process os digestion, aro astor Mds separated in thoid
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DE MULCENΤs.entire state hom the blood, by particular secreting organs. There is no gland whicli has this potver more particularlythan the kidneys ; substances received into the stomach and digested, afterwards pRSsing osr in the urine with ait theti peculiar properties. Sacchartae matter lar Oxample, thereis reason to belleve, can be Separated in this manner ; andit is equalty probabie, that mucilaginous or Oily Substances, whicli forin the principes demulcenis, are capable of such a separation. There ora be no doubi, however, but that agreat share of the relies demulcents afford in irritation, orinflammation of the urina passages, is o ving to the large
urine is diluted, and rendered tess stimulating. Porhaps theresios is to be ascribed solesy to this dilution; since no alteration is perceived in the quality of the urine, Dom tho use of these substances. And, in generat, demulcents may be Considered as substances tess stimulating than the fluids usuallyapplied to the paris that are in a state of irritation. Tho diseases in i ich demulcents are used, are principassycatarrh, diarrhoea, dysente , calculuS, and gonorrhoea. Theyare evidently not medicines of any great potver; they are oesy calculated to alleviate symptotus, and may be Deely used in as large quantities as the stomach ivili receive them. Demulcents may be arranged iinder ille two divisions of
some substances of a similar nature.
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GUM is a proximate vegetabie principie, whicli is sita ed by exudation, more Or less pure, Dom a number of planis. The Gum Arabic os commerce is not exclusively the produce of One vegetable : that whicli is most pure, and used to beimported DOm Egypt, is froni a species of mimosa. The London College admit, on the authority of Wildenow, a dinferent genus, A cacia, as substituted sor that of Mimosa; illey refer, theresere, to the species producing this gum by the name of Acacia Vera, and name the gum itself Gummi Acaciae, vhile the Edinburgii College nante it Gummi Mimoste Niloticae. The trivial name, Gummi Arabicum, is re-tained perhaps with propriety by the Dublin College. Thogreator part of the gum arabic os commerce, it appears, is imported Dom Barba , bcing the produce of Morocco, and principalty of the mouitiauis of Atlas. It is an exudation in the forna of a viscid pellucid juice, froin the bain of ilio trunk and branches of the tree, whicli hardens is exposure to the air and Sun. The purest gum of the shops is in Smallirregular pieceS, White or yelloavisti, scini-pellucid, without
iuste or smeli: there are Other varieties coarser, of a yello vor Ped colour; these are Sometimes named Gum Seneges,
and appear to be of different ori n. All of thom havo the properties of gum ; are insolubie in alkohol or Oils, and solubie in Water, forming a viscid solution named Muci lage. Cum Arabio is in common uso as a demulcent. In catari h it is allowed to dissolve sto vj in tho molith, and iis
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inucilage is the basis of the mixtures usualty employed toallay coughing. Sometimes, too, it is empl0yed in tenesmus,
a species under the name of A stragalus Tragacantha. ACCord-
ing to olivier, it is a disserent species, which he describes under the name of Astragalus Verus ; , and this is admitted by the London College. Tragacanth is tho produce of Persia indos Asia Minor ; it is in sinali wrintiled pieces, Semi-tranS- parent and britile, and has neither iaste nor smeli. It is regarded as a gum, yet it differs Boin the other pure gumsin not being persectly soluble in cold water : it is s0stenedand diffused, but romatiis flocculent and turbid. Whon heatis applied, it communicates to the water a great degree ofviscidity, but stili the solution remaliis turbid ; it appears, there re, to he intermediate between gum and secula. Itis greatly superior to est the gums, in giving viscidity to water ; iis power in this respect being to that of gum Arabicas I to 24. Ti'agacanth has virtuos similar to gum Arabic. It is tess
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486 DEMULCENTS. empl0ycd, excepi in somo pharinaceiatical proceSses, in Whicli, si om iis greator viscidity, it is preserrod, as in mining os
LINUM UsITATISsIMUM. Flax. Pentand. Pentagon. Gruinales. Semen. IndigenONS. ΓΗE seeds of this plant afford a strong mucilage by infusiouor decoction in water ; by expression they afford a quantityos Oil. This heing inferior in putity to the olive or almondoil, is lituo used in medicine. But the mucilage haring nounpleasant iaste or smeli, the infusion is frequently used as a demulcent in catarrh and gonori licea, being rendered more gratesul by the addition of a litile fugar and lemon juice. The decoction, containing a porti0n of the od diffused in thenaucllage, is tess gratesul. Ossio. Prep.-Insus. Liui. Lond. ALTHAEA OFFICINALIS. Althaea. IIarsh-mallow. Mona- delph. Polyand. Cohimnisci P. Brediar. Indigeristis. THIS indigenous plant grows, as the naine implies, in marshy Siluations. Ad the paris of it yielii a mucit e by infusion or decoction in mater: the root does sO most abundantly, xand frced Dom the outer bain, is hept in the Stiops. It is white, inodorous, and insipid. Iis nauci age is similario that froni sintsced, and is used for the sanae purpoSes. Itis even preser te, as being more pure. sic. Prop.-Decoct. Alth. Ed.-Syr. Alth. cd. LGns.
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DEMULCENTS. 487MALVA sYLVEsTRIS. Common Mallo v. M adelph. Polyand. Columniferae. Folia. Indigeri S. THE leaves of iliis plant assord a mucilago by infusion in Water, Whicli is weaher, however, than that from lintseedor althaea, and is theve re litile used. The leaves have also been used for the purpose of sementation, and their decoc
Papilionac. Nadiae. Soutis of Europe. ΤΗΕ ot of this plani, whicli is long, stender, and flexit,le,
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viriues of the root appear to reSide. Sarsaparilla produces no sensibie effect on the system, indit can scarcely be regarded in any other light than as a demulcent. It lias, however, been considered as a specific in the tueatinent of sonae venereat affections, particularly those of the bones or periosteum, and as a restorative in that State
os debility whicli is the consequence of the disea se protract-ed, or of the mercurial irritation. Without alto ng to itany specific power, it appears in Such cases to he sumetimes productive of benesit, probabb frona iis mild demulcent and nutritious quality, and paxtly perhaps froin the suspension os the use of mercury during iis administration. Ιt has also been
recommended in extensive ulceration, in culaneous affections,
Boiled in milla or wator, it dissolves entirely ; and this with fugar, and the addition frequently os a litile M ine, serius a