TANNIC ACID.—A substance obtained from oak-gall. It is a yellowish or white powder, having a bitter taste, and producing a sensation of constriction, dryness, and roughness in the mouth. Practically all the vegetable astringents depend for their action upon the presence of this acid or some of it derivatives. When tannic acid comes in contact with any albu men, it forms an insoluble compound. Thus, when it is applied to a mucous membrane, it combines to some extent with the albumen in the cells, so that they shrink and become hardened, and their secretion diminished. Tannic acid combines readily with the albumen of the blood, forming a clot, and is therefore used locally to arrest an oozing hxmorrhage. It has been given also internally for hxmorrhage of the stomach or bowels ; but it is of less service here, particularly in intestinal hxmorrhage. It is sometimes applied
to bleeding piles, either in an ointment or in a suppository. The constricting action of tannic acid is utilised in some forms of diarrhoea, being given by the mouth or used in enemas. It is used also in relaxed conditions of the nose, throat, and vagina. Tannic acid is an antidote for poisoning by any alkaloid. It may be given internally in ten-grain doses.
TANSY.—The leaves and tops of Tanacetmn vulgare, the common tansy. Its active principle is a volatile oil, °learnt lanaceli. It has a stimulating effect on the uterus, but it is uncertain and dangerous. Tansy-oil may cause violent abdominal pain, vomiting, unconsciousness, convulsions, and death. The uses of tansy are as a uterine tonic and for intestinal parasites. The infusion is commonly used in doses of one or two table spoonfuls.