Bistort: quasi bis torta; twice twisted, or wreathed. So called from the contortion of its roots. Called also the greater bistort, or snakeweed; colubrina, beadiramon. It is the poligonum bis-torta Lin. Sp. Pi. 516. Nat. order oleraceae.

It is perennial, a native of Britain, grows wild in moist meadows about Battersea, and by the side of Bishop's Wood near Hampstead, and flowers in May and June.

The root is bent vermicularly, and jointed at each bending. It is commonly about the thickness of a finger, surrounded with bushy fibres, of a blackish brown colour on the outside, and reddish within. It is distinguished from the other bistort roots by being less bent; that of the officinal species having only one or two bendings, and those of the other three or more.

This root is powerfully astringent, and as such antiseptic. It is of a singular efficacy in haemorrhage, obstinate fluxes, looseness of the teeth, spongy gums, and soreness in the mouth. It is said to be refrigerant; but this is from its being antacid, whence all astringents are cooling. The dose is from gr. x. to 3 i. Water totally dissolves its astringent matter. Extracts made with water, or with spirit, retain all the styptic qualities. All the parts of this plant possess the same qualities as the root, but in a less degree. If the roots are boiled in vinegar, an excellent antiseptic gargle is obtained. Dr. Cullen says it seems to be one of the strongest of our vegetable astringents, and justly commended for every virtue that has been ascribed to any other: he has frequently employed it in intermittents,and has given it both by itself and with gentian to the quantity of three drachms in one day. Cullen's Materia Medica.

The tormentil root is so similar in its efficacy, that it may always be substituted for it.

BlStoury. In surgeiy is a small knife, either straight or crooked, single or double edged, round pointed or probe pointed. Its form must be regulated by the purpose for which it is employed. Sometimes a director or a grooved canula is employed, along which the knife passes; and at others the instrument is concealed in a kind of sheath, which supplies the place of a director, and raised at the moment it is to be employed.