_a._ Its base, which should fit the hollow of the arm-pit. _b._ Its summit reversed, against which the elbow is to be applied. Fig. 2. The first roller applied for the purpose of fixing the bolster against the side of the thorax. _a a._ Oblique casts before, passing over the opposite shoulder, in order to hold it up. _b._ Oblique casts from behind, crossing the first ones on the shoulder. _d d._ Circular casts round the trunk, covering the bolster, which they fix laterally. Fig. 3. The second roller, applied to fix the arm against the bolster. _a & b._ Portions of the oblique casts of the first roller, left uncovered by this one. _c c._ Turns of the second roller, covering those of the first, loose above, and tighter below, for the purpose of drawing the superior extremity of the humerus outwards. _d._ Their passage over the side opposite to the bolster. Fig. 4. The third roller intended to keep the point of the shoulder raised. _a a & b._ Oblique casts of the first roller, remaining uncovered. _c c._ Turns of the second, seen through the opening of those of the third. _d._ Oblique casts of the third, ascending from the arm-pit over the shoulder of the diseased side, to descend again behind, along the arm, and pass under the elbow. _f k._ A continuation of the preceding casts, reascending under the sound arm-pit, and from thence behind the thorax, over the diseased shoulder. _e._ A continuation of the same casts, descending on the fore side of the arm, passing under the elbow, and ascending again under the arm-pit of the sound side. _g._ The remainder of the roller, intended to be employed in circular turns, in order to secure the casts _e_, and prevent them from slipping outward. Fig. 5. A sling which should be fastened to the oblique cast _d_ (Fig. 4), to support the hand. [Illustration: _Pl. 1_ _Fig. 1._ _Fig. 2._ _Fig. 3._ _Fig. 5._ _Fig. 4._ _Engrav'd by W. Kneafs._] MEMOIR III. ON THE LUXATION OF THE CLAVICLE. § I. 1. The clavicle, which forms a moveable abutment for the shoulder, and receives and sets bounds to most of the movements of that part, and of the arm, exhibits at its extremities, two articulations, essentially different from each other in their form, dispositions, and uses. These differences give rise to differences equally essential with regard to the dislocations to which they are subject. 2. On the sternal extremity, a small surface, convex from above downwards, and concave from before backwards, is fitted, by means of an intervening cartilage, to a much smaller surface of the sternum, concave and convex in opposite directions.