4. As the artery should never be raised from its bed, it is generally advisable to pass the needle only so far as just to permit the eye to be seen past the vessel. The ligature should then be seized by a pair of forceps and gently pulled through, the needle being cautiously withdrawn. When catgut is used, it is better to pass the unarmed needle till the eye is visible, then thread and withdraw it, thus pulling the catgut through. 5. As a rule, the needle should be passed from the side of the vessel at which the chief dangers exist. This will generally be in the side at which the vein is. 6. The ligature should be single, and consist of strong well-waxed silk, and should always be drawn as tight as possible, so as to divide the internal and middle coats of the vessel. In cases where the wound is to be treated with antiseptic precautions and an attempt at immediate union made, the ligature may be of strong catgut properly prepared, and both ends of it may be cut off. 7. Before the ligature is tightened, it is well to feel that pressure between the ligature and the finger arrests the pulsation of the tumour. LIGATURE OF THE AORTA.--It has been found necessary in a few rare cases to place a ligature on the abdominal aorta; no case has as yet survived the operation beyond a very few days, but they have in their progress sufficiently proved that the circulation can be carried on, and gangrene does not necessarily result even after such a decided interference with vascular supply. _Operation._--The ligature may be applied in one of two ways, the choice being influenced by the nature of the disease for which it is done. 1. A straight incision (Plate I. fig. 1) in the linea alba, just avoiding the umbilicus by a curve, and dividing the peritoneum, allows the intestines to be pushed aside, and the aorta exposed still covered by the peritoneum, as it lies in front of the lumbar vertebræ. The peritoneum must again be divided very cautiously at the point selected, and the aortic plexus of nerves carefully dissected off, in order that they may not be interfered with by the ligature. The ligature should then be passed round, tied, cut short, and the wound accurately sewed up. 2. Without wounding the peritoneum. A curved incision (Plate I. fig. 2), with its convexity backwards, from the projecting end of the tenth rib to a point a little in front of the anterior superior spinous process of the ilium. At first through the skin and fascia only, this incision must be continued through the muscles of the abdominal wall, one by one, till the transversalis fascia is exposed, which must then be scraped through very cautiously, so as not to injure the peritoneum, which is to be detached from the fascia covering the psoas and iliacus muscles, and must be held inwards and out of the way by bent copper spatulæ. The common iliac will then be felt pulsating, and on it the finger may easily be guided up until the aorta is reached.