TANNIN, PURE, or TANNIC ACID, Medical Properties of. This substance in combination with extractive has been long known under the name of tannin, and recognised as the active principle in almost all astringent vegetables. [ASTRINGENTS.] As many of these are powerful in restraining excessive discharges, whether bloody or otherwise, it was conjectured that the pure principle would be yet more efficacious than when in a state of combination. Accordingly it has been administered in some passive luemorrhnges, chiefly from the uterus and the bronchial tubes. To effect any good it requires to be given for several days in small doses. It is with difficulty absorbed into the circulation, being with great reluctance taken up by the lacteals, and producing very groat constipation, from its direct astrin gent action over the intestinal canal, with which it is brought into contact. Tannic acid has been recommended in cases of incurable organic diseases affecting the uterus, accompanied with ,wasting dis charges. These it may for a time moderate, but the tenistipation
induced never fails ultimately to aggravate the disease and disoomfort of the patient. There is little therefore to induce practitimers to employ it to act on remote organs, as it appears to be converted into gallie acid wherever it is absorbed. To facilitate its action a solution of it In alcohol, or, Letter rold,riii ether is employed. This is a very powerful topical astringent. Tannin present in the after-meth of grasses given u food for cattle seems to pass out almost unchanged, and in the putntity originally It is of use, along with the bitter extractive, in restraining the fermentation of the food. It is its presence in vegetables which causes the motion, to become black when any preparation of iron or chalybeate water is takeu.