29. Desault cautioned his pupils not to confound this last sign or symptom with a kind of noise, sometimes heard in the sheaths of the tendons of the extensor longus, extensor brevis, and abductor longus; a noise resulting from a filtration of synovial fluid into the sheaths, or produced by some other cause. But, besides this crepitus in the sheaths being a very rare occurrence, it is always easy to distinguish it from a crepitation of the bone, by this circumstance, that the first is heard on merely pressing the parts, but the latter only by making the bony surfaces rub against each other. Besides, by an experienced ear there is no danger of any mistake being committed. 30. If the fracture exist at the upper end, the thick muscular covering which there surrounds the radius, renders the diagnosis more difficult. Petit has, however, thrown some light on the subject, by judiciously advising to place one hand on the upper extremity of the radius, and with the other to make the fore-arm rotate on this bone. The solution of continuity or fracture will be rendered evident, if, in the midst of these motions, the head remain stationary. But if, on the other hand, it rotate, it has sustained no injury. These two circumstances can be easily explained; but, it is not so easy for the practitioner to avail himself of them in every case. This precept may also be applied in cases where a considerable swelling, occupying the whole fore-arm, conceals from the touch of the surgeon the fragments of the bone, even when broken in the middle. § IX. OF THE REDUCTION, AND THE MEANS OF MAINTAINING IT. 31. The reduction of a fracture of the radius is effected in nearly the manner already described for that of the two bones of the fore-arm (10–13), except that, here, the extension must be less, because there exists no displacement in a longitudinal direction (26). To remove that which exists in a cross direction, an assistant whose business it is to make extension, places the hand in a state of adduction, for the purpose of removing the inferior fragment outwards. This precept cannot be applied to much advantage, if the division exist towards the upper end, on account of the interosseous ligament. At the same time the surgeon endeavours to bring the ends of the bone into perfect contact, by pushing them in a direction opposite to that of their displacement; and when he has attained this end, he begins the application of a bandage or apparatus the same as that already described (19 and 20), with this difference, that as the ulna is here sound, and performs, in relation to the fractured radius, the office of a natural splint, it is unnecessary to place an artificial one between the internal condyl of the humerus, and the styloid apophysis of the ulna.