26. The reduction, in this case, is generally attended with but little difficulty. The acromion being drawn outward, by the upper end of the os humeri, which, by means of a fulcrum placed under the armpit, is made to act as a lever of the first kind, is restored, without much trouble, to its natural contact with the corresponding surface of the clavicle. But, it soon becomes deranged again, unless it be retained in its place by a proper apparatus. Now, on what principle ought this apparatus to be constructed? To prevent the displacement, which generally occurs from without inwards, it ought evidently to act from within outwards. Whence it follows, that the rollers in the figure of 8 bandage, recommended in this case by all writers, instead of preventing, actually favour the displacement (17), because they act in the same direction with, and therefore assist, the powers that produce it. 27. Here, in like manner as in the preceding case, the bandage of Desault fulfils with precision the indications of cure, because, by it, the point of the shoulder is, particularly, drawn outward; and if, in certain cases, a slight projection of the humeral extremity still remains, it is to be attributed to the inefficacy of the means of execution, and not to the principles on which they are founded. MEMOIR IV. ON FRACTURES OF THE ACROMION, AND OF THE LOWER ANGLE OF THE SCAPULA. § I. FRACTURE OF THE ACROMION. 1. There is no part of the scapula more liable to fractures than the acromion. Being but slightly covered by the soft parts, this insulated kind of appendix has not, in all positions of the humerus, a solid point of support. A strong muscular force oftentimes acts on it with great energy. Being large in front, it presents in that direction a considerable surface to receive the action of external bodies. Whence it follows, that if it is not oftentimes broken, this is to be attributed, not so much to its natural disposition, as to the position which it generally assumes in falls. 2. The fracture, which is almost always transverse, is sometimes at the summit, and sometimes at the base of this apophysis, and is usually produced by a violent shock from a body falling on the shoulder, by a blow received on that part, &c. 3. But in whatever place it occurs, it greatly resembles a fracture of the humeral extremity of the clavicle, of which the acromion appears like a continuation. There is accordingly a strong analogy between the phenomena, the consequences, and the modes of treating these two kinds of fractures.