PLASTERS (AS. plaster, OlIG. pflastar, Ger. from OF. plus! re, plaietre, em piastre, Fr. phitrc. emphit re, from Lat. on plastrum, from GI:. garNaorpov, (It/phis/run, empiaston, plaster, from emplassein, to plaster, from iv, en, in + plassein, to form). Tenacious preparations for external application, solid at ordinary temperatures, but pliable and adhesive at the temperature of the body. Most plasters have as their base a compound of olive oil and litharge, constituting the lead plaster of the pharmacopreia; others owe their consistence and adhesiveness to resinous substances. a mixture of these with wax and fats. These stances, alone or impregnated with medieinally active materials, are spread in a thin layer upon linen, muslin, or leather. Formerly this ing was done by hand. but of late years the work is accomplished entirely by machinery, which tributes the plaster mass with great evenness, and perforates or makes porous the finished product. Sinee the introduction of machinery has been largely employed in the adhesive composition. There are thirteen
ters recognized by the United States pivia: lead, ammonia and mercury, iron, Inereury, opium, soap. resin. arnica, capsicum, belladonna, pitch, isinglass. and cantharides, besides many unollieial varieties. Besides their generally tective properties, these plasters have special therapeutic actions dependent upon the active ingredient. Opium plaster, for example, is dyne. as is also belladonna; lead and arnica are soothing and astringent; mercury, alterative; capsicum is used as a and tharides as a agent. Court plaster consists of a solution of isinglass thinly spread upon silk. previously coated with tincture of zoin. It is employed as a dressing to protect slight cuts or abrasions and must be moistened before application. skin is larly used. In surgery adhesive plaster is sively used for its mechanical effect to reEnforce weak muscles, to keep dressings in place, to cover ulcers, to limit effusions, etc.