That the Lateral Movement of the Ulna in Pronation and Supination Takes Place at the Shoulder-Joint

place a finger on the styloid process of the ulna, and then pronate in the ordinary way, it will be quite evident that the bony point moves from its place. It will return again when the hand is again supinated. 2. Lecomte's Ring Experiment.?If the radius alone moves, then, since the axis of movement at the wrist passes through the head of the ulna,1 the transverse diameter of the forearm there will be only about half of the diameter of the circle, part of whose circumference is traversed by the styloid process of the radius in pronation and supination. In other words, so long as the ulna is stationary, it will be impossible to rotate the wrist within a ring whose diameter is only slightly greater than that of the wrist itself. If, on the other hand, the ulna be moving in the reverse direction to that taken by the radius, the real axis of movement will be thrown more into the centre of the forearm, and the styloid process of the radius will traverse part of the circumference of a much smaller circle than it would otherwise do. Lecomte2