29. For the purpose of making extension, he used the foot as a lever of the first kind. The two hands of an assistant, grasping it in such a manner, as to make the fingers cross on the back of it, while the thumbs, also crossing each other, corresponded to the sole, represented the power; the articulation represented the centre of motion, or fulcrum, and the leg together with the lower fragment, the resistance. The requisite motion was then communicated to the foot, and in that way was the extension effected. This mode is more advantageous than that usually employed, where the hands are applied to the lower extremity of the leg; for the force of the extending power is generally in the inverse ratio of its distance from the resistance intended to be overcome. 30. What I have said of extension (28), applies also to counter-extension. The strap, which was formerly placed for this purpose in the groin of the affected side, by compressing the adductores, and the rectus internus, produced in them a contraction, which, by drawing the lower fragment towards the pelvis, opposed obstacles to the reduction, which are seldom experienced, when, like Desault, the surgeon contents himself with having the trunk held by assistants, either exclusively at the hips, or both at the hips and under the arm-pits. The resistance being always easily overcome in this affection, renders it unnecessary to have recourse to more powerful means. 31. Hippocrates advises, in fractures of the os femoris, to aid extension by coaptation, performed with the hand. All practitioners, since his time, have added this third manœuvre or process to the two first, namely, extension and counter-extension. But, what effect can the hands produce, in most cases, on the bone through the thick covering of the soft parts? Are we able to communicate to it through such a mass whatever lateral movement we please? Being quite lost in the intervening soft parts, will our efforts reach the bone, in the direction which we give them? The muscles bring the fragments into contact, much better than we can, as soon as extension has removed their overlapping. Indeed, if well executed extension makes the lower fragment return along the same track which it pursued in becoming displaced, it will then be inevitably brought into contact with the upper one by the contraction of the muscles. Besides, in most oblique fractures, is it not evident, that the lower fragment must be made to slide from above downward, on the inclined plain presented by the upper one, and on which it has slided from below upward, in becoming displaced? Is it while extension is making that coaptation ought to be performed? Certainly not: because, if the extension be well directed, an attempt at coaptation will derange it; and if it be not well directed, its course ought to be changed. Is it after extension is finished that recourse ought to be had to coaptation? By no means: