16. All kinds of apparatus for fractures, being nothing but resistances opposed by art, to the powers which produce displacement, it follows, that they should all act in directions precisely opposed to the directions of those powers. But, we have seen (7), that, in the present case, these powers are, 1st, the action of external bodies, favoured by the extreme mobility of the arm and shoulder; 2dly, the action of the latissimus dorsi, the pectoralis major, and the teres major, which carry the inferior fragment inward, or, what is more common, of the deltoid muscle, which draws it outward; 3dly, the contractions of the muscles of the arm, which have a slight tendency to draw the same fragment upwards. 17. Therefore, 1st, to render the arm and shoulder immoveable; 2dly, to carry the upper end of the lower fragment outward or inward, according to the direction in which it is displaced; and, 3dly, to draw this fragment downward, are the three indications that ought to be fulfilled by every bandage intended for a fracture of the neck of the humerus. The last merits less attention than the other two, because, as already observed, the weight of the limb alone is nearly sufficient to answer it. 18. Let us inquire, whether or not the kinds of apparatus, hitherto employed, have been adequate to the fulfilment of these indications. The ancients, in obedience to the precept of Hippocrates, fixed the arm against the breast, and confined it there by a bandage recommended by Celsus, and constantly employed by Paul of Egina. “_Præstat antem_, says he, _brachium, ad thoracem moderate deligare, ut ne, si id commoveatur, figuram avertat_.” Pare still preserved this process, which the moderns have now entirely abandoned, and which, taken alone, could properly fulfil only the first indication. The second indication was less happily fulfilled, by a kind of bandage added to the first, by Celsus, Paul of Egina, and the Arabians, the necessary effect of which was, to force the lower fragment outwards. It is surprising that Heister and Lamotte should have confined themselves to the use of this for the retention of the fragments. What shall we say of the eighteen-tailed bandage exclusively adopted by Petit and Duverney? The arm, not being fixed by it, was liable to be moved, and the fragments to be displaced by the least shock. There was nothing to prevent the lower fragment from obeying the powers tending to carry it either inward or outward. Indeed the bandage was of no avail whatever in giving support to a fracture, as was observed by Louis, in his “Dissertation on Petit’s Diseases of the Bones.” Suppose the arm, as some have advised, to be supported only by a sling. Not one of the indications just established (17) could by such means be fulfilled.