It is of the utmost importance for the safety of the operation and the patient's comfort after it, that the rectum be completely unloaded before the operation, and the bowels so far emptied as to permit three or four days after the operation to elapse without any movement of the bowels being necessary. If there is any doubt as to the effect of the laxative, a large stimulant enema should be administered on the morning of the operation. _Position._--Much depends on the proper tying up of the patient. He should be placed with his breech projecting over the edge of a narrow table, with head slightly raised on a pillow, but the shoulders low. The hands are then to be secured each to its corresponding foot, by a strong bandage passing round wrist and instep, or by suitable leather anklets, the knees should be wide apart, and on exactly the same level, so that the pelvis may be quite straight. An assistant should be placed to take charge of each leg. The staff is next introduced and the stone felt; if there is little water in the bladder a few ounces may be injected, but this is rarely necessary, for the patient should be ordered to retain as much water as possible, and when he cannot retain it, injection of water may do harm, and will probably not be retained, but at once come away along the groove in the staff. The staff is then committed to a special assistant, who must be thoroughly up to his duty, and attend to the staff alone. Some surgeons direct the assistant to make the convexity of the staff bulge in the perineum, to enable the groove to be struck more easily. It will be, however, safer both for the rectum and the bulb, if the staff be hooked firmly up against the symphysis pubis, as advised by Liston. The same assistant can also keep the scrotum up out of the way. If the perineum has not been previously shaved, this is now done. The operator sits down on a low stool in front of the patient's breech, his instruments being ready to his hand, and then steadying the skin of the perineum with the fingers of his left hand, enters the point of the knife in the raphe of the perineum, midway between the anus and scrotum (one inch in front of anus--_Cheselden_, _Crichton_; one and a quarter--_Gross_, _Skey_, and _Brodie_; one and three-quarters--_Fergusson_; one inch behind the scrotum--_Liston_), and carries the incision obliquely downwards and outwards, in a line midway between the anus and tuberosity of the ischium. The length of the incision must vary with the size of the perineum, and the supposed size of the stone, but there is less risk in its being too large, so long as the rectum is safe, than in its being too small. Its depth should be greatest at its upper angle, where it has to divide the parts to the depth of the transverse muscle of the perineum, and least at its lower angle, where a deep incision is not required, and would be almost sure to wound the rectum.