The reason of this may be found in the nature of the flap itself, originally intended to bear the weight of the body, there being no cicatrix at the part on which pressure is borne. I have noticed that perfection in walking on an ankle-joint stump has a certain relation to the freedom of movement which the pad has over the face of the bone. This ought to be pretty considerable. It is explained by the new attachments formed by the tendons, and is under the control of the patient, being elicited when he is told to move his toes. It has been objected to this operation that the flap is apt to slough. When improperly performed, as when the flap is scored transversely in its separation, and especially when the flap is cut too long (as has been already noticed), this may occur; but that there is nothing whatever in the position or condition of the flap itself that at all necessitates its sloughing, is thoroughly proved by the following remarkable case, given by Mr. Syme in his volume of _Observations in Clinical Surgery_. I quote it entire:-- "P.C., aged thirty-three, was admitted into the hospital on the 25th July 1860, in the following state:--He had been treated in the Manchester Infirmary for popliteal aneurism by pressure, so decidedly applied that it had caused an ulcer, of which the cicatrix remained; but without producing the effect desired. The femoral artery was then tied with success, in so far as the aneurism was concerned, but with the unpleasant sequel, some months afterwards, of mortification in the foot, which was thrown off, with the exception of the astragalus and os calcis with their integuments, a large raw surface being presented in front where the bone was bare. Although the patient was extremely weak, and the parts concerned might be supposed more than usually disposed to slough, I did not hesitate to perform the operation, with the speedy result of a most excellent stump and complete restoration to health."--Pp. 49, 50. The modifications of Mr. Syme's original operation have been very various. It will be unnecessary even to name them all. One or two may require notice. Retaining Mr. Syme's incisions in their integrity, some operators prefer not to disarticulate the foot, but remove it by sawing through the tibia and fibula at once, while still in connection with the foot. That most excellent surgeon and first-rate operator, Dr. Johnston of Montrose, used to prefer this method.