11. The displacement here is, in general, inconsiderable, because, being drawn in contrary directions, by the muscles of the arm and fore-arm, the condyls separated from the bone remain stationary between these two forces. A fall, a percussion, or some other external cause, can alone produce a displacement, by communicating some degree of motion to the fragments. Now, from what was formerly said (5 & 6), the condyls may, under such an impulse, move either forward or backward, or else may separate from each other, leaving between them an intermediate void. Hence the apparatus ought to oppose to them a resistance in these four directions, namely, inward, outward, forward, and backward; a resistance which it will be easy to make, by means of four splints, placed in these directions, and properly retained by a roller. The two lateral splints, are particularly necessary, when the condyls are both separated from the body of the bone, and divided from each other (3). If one of them be still attached to the humerus (4), a splint on that side becomes less useful. 12. It is needless for the apparatus to extend as high up as in a fracture of the arm. What effect, in sustaining the fragments, would casts of a roller have, when applied to the body of the bone, above the place of division? Their only advantage would consist in compressing the brachial and triceps muscles, and in that way preventing their action. On the other hand, the roller must be continued along the fore-arm, in order that the elbow joint may correspond, according to the judicious precept of Paul of Egina, to the middle of the bandage, which is in general more compact and solid, in the middle than in any other part, and also, that a slight compression may be thus made on the muscles attached to the condyls. 13. The pieces which compose the apparatus, are 1st, A roller five or six yards long, and three inches broad, made of soft linen or muslin, and rolled up in a ball. 2dly, Four splints (11), two of them flexible in the middle, in order that they may bend to fit the fold of the arm, and the elbow, and the other two very strong and inflexible, intended to be applied at the two sides.