73. Complicated fractures of the os femoris, being included in the general class of solutions of continuity of that description, cannot be at present particularly considered. We will only remark, that here, in like manner, as in fractures of the clavicle, permanent extension constitutes the most effectual method of preventing the pains, oftentimes insupportable, occasioned by splinters or points of bone irritating the soft parts, from being pressed against them by muscular action in its tendency to shorten the limb. § IX. OF PERMANENT EXTENSION IN OLD FRACTURES. 74. I will close this article by a few remarks on the advantages of permanent extension in old fractures. Nature reunites fractures differently, according to the relation of the divided surfaces to each other. Are those surfaces in perfect contact? If so, they are chiefly instrumental in the formation of callus, which then probably acts in a manner similar to the reunion of wounds. On the other hand, does an overlapping of the fragments separate the divided surfaces from each other; the reunion takes place then principally on the sides, by a kind of enlargement of the bones, produced no doubt by the periosteum. Such is the mode of consolidation, which, on opening dead bodies, is found in most oblique fractures of the os femoris, succeeded by a shortening of the limb. 75. Hence it follows, that this shortening, which would readily yield to extension, at the time of the fracture, becomes obstinate in its resistance, in proportion to the age of the accident. In such a case, indeed, the substances destined to reunite the overlapping fragments, acquiring daily more and more solidity, oppose to the reduction obstacles constantly increasing. Hence, most practitioners regard this reduction as beyond the resources of art, after the expiration of the twelfth or fifteenth day. Nor is this opinion entertained without some foundation, for at a later period, almost all efforts at reduction, however powerful, have proved unavailing. But that which cannot be performed by a very powerful effort, acting momentarily, is, notwithstanding, oftentimes easily attainable by a much weaker one, provided it be long continued. The following cases are in proof of this. CASE III. Ann Gallot, of Melun, aged sixty-nine, having fractured her right thigh, by falling down the steps of a cellar, remained twenty-two days without assistance, and without even knowing the nature of the accident, when, on consulting a surgeon, she was sent to the hospital at Versailles. From the long standing of the disease, a reduction being despaired of, and no one being willing even to undertake it, the patient was sent to the Hotel-Dieu, on the 27th of February, 1791.