TOURNIQUET, an instrument for compressing the main artery of the thigh or arm, either for the purpose of preventing too great it foss of blood in amputation, or to check dangerous hemorrhage from accidental wounds, or to stop the circulatiou through an aneurism.
The common tourniquet consists of three parts—viz., (1) a pad to compress the artery; (2) a strong band which is buckled round the limb; and (3) a bridge-like con trivance over which the band passes, with a screw whose action raises the bridge and consequently tightens the band. The best kind of pad is a small firm roller about an inch thick; it must be placed lengthways over the main artery so as to compress it against the bone, and most be secured in its place by a turn of bandage, over which the band of the tourniquet must be applied. This hand must first. be tightly buckled, and the pressure must be then increased to the necessary extent (namely, till the beating of the artery beyond the instrument ceases to be perceptible) by the action of the screw.
which should always be opposite the buckle of the band. As the instrument arrests the venous blood, it should never be applied tightly in cases of amputation, until the sur geon is ready to make his incision, as otherwise there would be an excessive loss of venous blood.
The credit of the invention of this most useful instrument is usually ascribed to the French surgeon, Morel, who, in 1674, used a stick passed beneath a fillet, and turned round so as to twist it up to the requisite degree of tightness, as a means of preventing the undue loss of arterial blood in amputatioas of the limbs—a rough, but by no means ineffectual form of tourniquet, which may often be usefully extemporized in cases of emergency at the present time. Mr. Young, of Plymouth, in 1679, described a similar apparatus. A much improved screw tourniquet was invented by Petit early in the fol lowing century.