21. But we are not to suppose, that these processes have heretofore manifested an exact application of this rule. Hippocrates directed to press the arm close to the ribs, and at the same time to push it upwards, in such a manner, as to make the shoulder appear as sharp and pointed as possible. Hence his precept, to lay the patient down on his back, the back being supported by some projecting body, and then to press the shoulders backward; hence again, when the humeral fragment is drawn inward, his advice to press the elbow close to the breast. This twofold expedient was attended with great difficulties, even under the direction of the father of medicine. Celsus only copied Hippocrates, adding nothing whatever to his mode of practice. Paul of Egina, more judicious in this case, conceived, that for the purpose of forcing the shoulder outward, and rendering it, agreeably to the idea of Hippocrates, very projecting and sharp, it would be advisable to place the fulcrum or point of support, not in the middle of the back, but under the arm-pit. A woollen ball was employed by him for this purpose, a practice which would, at once, have carried the art near to perfection, if, after being employed to reduce the fragments, this process had been continued for the purpose of retaining them in apposition. 22. No new method distinguished the surgery of the Arabians. It is necessary to come down to the time of Guy of Chauliac, before we meet with the method which is almost universally adopted at present, and which consists in placing between the shoulders, the knee of an assistant, whose hands are to be employed in drawing them forcibly backwards. But it is evident that this is only doing, while the patient is in an erect position, what Hippocrates did, after having laid him with his back on a projecting body. Here, then, the art seems to have degenerated, after the time of Paul of Egina: and, indeed, on comparing this process with the general principles already established (20), it will be immediately perceived, that the powers of replacement do not here act in an opposite direction to those of displacement. Hence the difficulties of reduction, the time spent in the operation, and the sufferings by which it was sure to be accompanied. The fragments were brought together, it is true; but it was only by varying the movements, and changing their direction, that the point of contact was ultimately found. 23. Desault conceived, in the year 1768, that to reduce, in the most effectual manner, a fracture of the clavicle, it was necessary not only to push the shoulder backward and upward, as was commonly done, but, above all, to force it outward, and that the power destined to draw it in this latter direction, ought to act horizontally, according to the course of the clavicle, in the same way, as, in an oblique fracture of the thigh or leg, the extension for replacing the fragments is made in the direction of the bone.