6. A hook, fitted with a buckle and strap, and hinged so that, by turning a pin, it at once disengages itself. If this is interposed between the pulleys and the hook fixed in the wall, the limb may be instantaneously released if desired. [Illustration: Fig. 66.—Dislocation of the dorsum ilii.] _Treatment._—Step 1. The patient is laid on a flat couch, and put under the influence of chloroform. When he is narcotised, a jack towel, or if it be at hand the pelvic girdle, is carried across the perinæum, arranging it to bear on the tuber ischii behind and the pubes in front, its ends being attached to one of the hooks screwed into the wall behind, and about six inches below the level of the patient. This towel should be put slightly on the stretch, that the pelvis may be kept in the position first assigned to it when the pulleys begin to draw. A wet roller is put on the lower third of the thigh, the jack towel slipped up the leg to the bandage, and fastened in a clove hitch. Another jack towel is then doubled and passed up the limb to the perinæum. The patient is next turned on to his sound side, and the belt of the thigh connected by the disengaging hook to the pulleys, which are drawn out from each other as far as their cord will allow, and attached to a hook fixed a little above the level of the patient, on a line carried from the hip across the junction of the middle and lower thirds of the uninjured thigh (see fig. 66). Step 2. The surgeon being ready, an assistant draws on the pulley cord, getting gradual extension of the limb as required by the surgeon, who, keeping his hands on the hip and great trochanter, watches the progress of the head of the bone towards the acetabulum. Step 3. When the bone has reached the edge of the acetabulum, a second assistant slips the doubled jack-towel over his shoulders, and by raising his body, lifts the femur away from the brim of the acetabulum, while the surgeon, grasping the foot and knee, makes a few movements of rotation backwards and forwards to ease the head into its socket. When a reduction is effected, the limb should be put in a long splint or starch bandage for three weeks, and the patient not allowed to exercise the limb freely or violently for a month afterwards. _Reduction by Manipulation._—When the patient is not very muscular, and the dislocation recent, the bone can often be speedily returned by movements of flexion and rotation.