4. In such a case, what is the first and most obvious indication? It is necessary to increase the extent of the opening in the capsule, by moving the limb in every direction. Some persons have deemed it impossible to tear this membrane anew. But, if we recollect, that the neck of the os femoris, being placed between the edges of the opening, must necessarily draw them asunder by the motions impressed on it, it is easy to conceive, that the angles, where these edges unite, will be torn, if the motions be carried to an inordinate degree: besides, experience proves here, as well as with regard to the humerus, the truth of the doctrine contended for. Are we to apprehend, as these same persons will have it, that serious accidents may be produced by such violent motions? Experience again answers in the negative. Nothing, then, can be more certain, than that this observation, respecting the opening in the capsule, is a great stride towards perfection in the treatment of luxations in general, and particularly of that now under consideration. 5. When this obstacle to reduction has been removed, it is then very readily effected, and that without the process of conformation. Indeed that process is almost always unnecessary. For what purpose should it be employed? Is it to increase the effect of extension, and thus disengage the head of the bone from the place which it accidentally occupies? In this point of view, it is nothing but a very feeble force, added to a very powerful one, which receives from it, therefore, but little assistance: it is much better, if necessary, to augment the extending forces themselves. Is it to push the head of the bone into its cavity, after the extensions have dislodged it? It is to the muscles, and not to the efforts of the surgeon, that the performance of this office belongs. Indeed, the surgeon must act altogether in the dark in this respect, as he cannot possibly ascertain the precise point where the opening in the capsule exists: he may, therefore, even push the head of the bone against a sound part of the capsule, and thus himself create an obstacle to the reduction, which he is attempting to favour. 6. The muscles, on the other hand, by their contraction, naturally draw the head of the bone into its place, because the direction of their fibres is such as obliges them to do it. The great art of managing luxations, then, consists, in ascertaining clearly the obstacles that prevent reduction, in removing them, and, then, committing the rest to extension, and the powers of nature properly directed. MEMOIR XII. ON SPONTANEOUS LUXATIONS OF THE OS FEMORIS.