Plasters

Plasters are a class of medicinal agents consisting of 'adhesive substances, spread upon leather or cloth, so as to stick to the part of the body to which they are applied.' The plasters of the British Pharmacopœia owe their adhesiveness either to a combination of oxide of lead with fatty acids, or to the presence of a tenacious resin, or to both. The most important are lead plaster, or diachylon, which enters into the composition of many of the others; resin and pitch plasters; belladonna and opium plasters; mercury and ammoniacum and mercury plasters; and cantharides or blistering plaster. Some of the most tenaciously adhesive of plasters (not in the Pharmacopœia) are made with preparations of india-rubber. Court or sticking plaster, for dressing slight wounds, consists of a thin layer of isinglass spread upon silk, and differs from the others mentioned in requiring to be softened with warm water before it will adhere; Goldbeater's Skin (q.v.) is also used for the same purpose. They are employed with two distinct aims—viz. to act mechanically, as by affording artificial support to weak muscular structures, by preventing threatened or tedious excoriations, by protecting parts already excoriated from the action of the air, &c.; and to act medicinally as counter-irritant, stimulant, discutient, alterative, anodyne, &c.