BENJAMIN BELL'S FLAP OPERATION ABOVE THE KNEE (reported in his own words, slightly abbreviated).--"When this operation is to be performed above the knee, it may be done either with one or two flaps, but it will commonly succeed best with one. The flap answers best on the fore part of the thigh, for here there is a sufficiency of the parts for covering the bones, and the matter passes more freely off than when the flap is formed behind.... The extreme point of the flap should reach to the end of the limb, unless the teguments are in any part diseased, in which case it must terminate where the disease begins, and its base should be where the bone is to be sawn. This will determine the length of the flap, and we should be directed with respect to the breadth of it by the circumference of the limb, for the diameter of a circle being somewhat less than a third of its circumference, although a limb may not be exactly circular, yet by attention to this we may ascertain with sufficient exactness the size of a flap for covering a stump (Plate IV. fig. 17). Thus a flap of four inches and a quarter in length will reach completely across a stump whose circumference is twelve inches; but as some allowance must be made for the quantity of skin and muscles that may be saved on the opposite side of the limb, by cutting them in the manner I have directed, and drawing them up before sawing the bone, and as it is a point of importance to leave the limb as long as possible, instead of four inches and a quarter, a limb of this size, when the first incision is managed in this manner, will not require a flap longer than three inches and a quarter, and so in proportion, according to the size of the limb. The flap at its base should be as broad as the breadth of the limb will permit, and should be continued nearly, although not altogether, of the same breadth till within a little of its termination, where it should be rounded off so as to correspond as exactly as may be with the figure of the sore on the back part of the limb. This being marked out, the surgeon, standing on the outside of the limb, should push a straight double-edged knife with a sharp point to the depth of the bone, by entering the point of it at the outside of the base of the intended flap; and carrying the point close to the bone, it must here be pushed through the teguments at the mark on the opposite side. The edge of the knife must now be carried downwards in such a direction as to form the flap, according to the figure marked out; and as it draws toward the end, the edge of it should be somewhat raised from the bone, so as to make the extremity of the flap thinner than the base, by which it will apply with more neatness to the surface of the sore. The flap being supported by an assistant, the teguments and muscles of the other parts of the limb should, by one stroke of the knife, be cut down to the bone, about an inch beneath where the bone is to be sawn; and the