Tourniquet, in surgery, an instrument composed of rollers, screws, straps, etc. for the purpose of compressing a limb, or other part of the body; in order to prevent too great an effusion of blood from wounds.

The tourniquet is one of the best contrivances in the art of healing : by compressing the blood vessels, it may be so regulated, as completely to check the farther efflux of that vital fluid, from wounded parts ; and thus frequently to save a valuable life.

Without entering into a description of the various improvements that have lately been introduced into this essential part of operative surgery, we cannot omit to re-commend to our readers, who are situated at a distance from professional aid, to provide themselves with this simple and Useful instrument, which may be had, in the greatest perfection, of Mr. Sa-vigny, whom we have, often mentioned on similar occasions. To persons travelling, or inhabiting warm climates, a tourniquet may prove of the greatest advantage; and we conceive it to be one of the most necessary articles in a medicine-chest, as well as in a case of instruments.

Where it becomes an object of importance, to suppress the bleeding from arteries of the lower extremities, without intercepting the circulation through the whole limb, the following ingenious method of applying a tourniquet has been recommanded, as perfectly fafe, by a skilful young surgeon in the metropolis. After providing a hard roll of linen bandage, about 4 or 5 inches in width, and 3 in thickness, as likewise a smooth board, 9 inches in length, 3 in width, and 3/4 of an inch in thickness, with the sides and ends squared at right angles; .the roller is to be placed mid-way in the ham on the under sides of the knee-joint; the leg being extended in a straight line. Next, the piece of board must be laid over the roller, which is to aft as a pad of compression on the popliteal artery that extends from the ham over the hollow of the knee; the length of the board running cross-ways, and projecting on the knee-joint on each side. Now, the girth of the tourniquet is to go round the knee- above (not upon) the knee-pan, and over the projecting ends of the board. The screw should rest at the upper part of the limb and the knee-pan, having also a pad interposed between it and the skin. By this mode of compressing the popliteal artery, an important advantage is gained , because it allows the arterial circulation to proceed uninterrupted through the lateral branching vessels ; the large superficial veins are not disturbed; and the limb remains in the same state as if the artery alone had been tied. - In all cases of profuse hemorrhages, when there is a chance of saving the limb, such method of applying the common tourniquet, will be preferable to the usual manner, by which the circulation of the blood is entirely stopped. Farther, in gun-shot wounds, compound fractures, and secondary bleedings after amputation below the knee, the practice here suggested will generally be attended with the desired effect.

Having thus enlarged upon a subject, which materially relates to the safety of every individual, we shall only add (as supplementary to the article Styptic), that in accidental injuries, or wounds attended with profuse bleeding from large blood-vessels, we are not acquainted with a more simple and effectual remedy than the Powder of Gum Arabic. This mild application to the orifice of the vein, or artery, speedily forms an incrustation around the part affected; especially if it be immediately strewed over the spot from which the blood issues; and if the contiguous muscles be at the same time gently compressed, till a proper bandage, roller, or tourniquet, can be procured.