the ligature, avoid as far as possible bifurcations, or the neighbourhood of large collateral branches.

2. A free incision should be made through the skin and subjacent textures, till the sheath of the artery is reached and fairly exposed.

3. The sheath must be opened and the artery cleaned with a sharp knife till the white external coat is clearly seen. The portion cleaned should, however, be as small as possible, consistent with thorough exposure, so that the ligature may be passed round the vessel without force.

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 The ligature should then be seized by a pair of forceps and gently pulled through, the needle being cautiously withdrawn.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.

The really difficult part of the operation now begins: to isolate the vessel from the spine behind, the inferior cava on the right side, and the plexus of nerves in the cellular tissue all round. The cleaning of the vessel must be done in great measure by the finger-nail, and much dexterity will be required to pass the ligature without unnecessarily raising the vessel from its bed, especially as the vessel itself may very possibly be diseased, and the aneurism of the iliac trunk for which the operation is required will displace and confuse the parts, and may have set up adhesive inflammation.

Results.—Operation has been performed at least ten times. By the first method by Sir Astley Cooper and Mr. James; by the second by Drs. Murray and Monteiro, M'Guire, Heron Watson, and Stokes, and Mr. South, and Czerny of Heidelberg. All the cases proved fatal; Dr. Monteiro's survived for ten days, and eventually perished from hæmorrhage; the rest all died at shorter intervals.

Ligature of Common Iliac.—Anatomical Note.—This short thick trunk varies slightly in its relations on the two sides of the body. As the aorta bifurcates on the left side of the body of the fourth lumbar vertebra, the common iliac of the right side would have a longer course to pursue than that on the left, if both ended at corresponding points. However, this is not always the case, as has been pointed out by Mr. Adams of Dublin, as the right common iliac often bifurcates sooner than the left does. With this slight difference, the position of the two vessels is precisely similar, each extending along the brim of the pelvis from the bifurcation of the aorta towards the sacro-iliac synchondrosis for about two inches. Sometimes the division takes place a little higher, even at the junction of the last lumbar vertebra and the sacrum. This variation depends chiefly on the length of the artery, which, as Quain has shown, varies from one inch and a half to more than three inches.

The anterior surface of both arteries is covered by the peritoneum, and each is crossed by the ureter just as it bifurcates into its branches.

The artery of the right side is in close contact behind with its corresponding vein, which at its upper part projects to the outside, and below to the inner side. The artery of the left side is less involved with its vein, which lies below it, and to the inside. The right is in contact with a coil of ileum, the left with the colon. The inferior mesenteric artery crosses the left one, while to the outside of both, and behind them, lie the sympathetic and obdurator nerves.

There are no named branches from the common iliac.

Operation.—The chief difficulties to be encountered are—1. The close proximity of the peritoneum, and specially the risk there is that it has become adherent to the sac of the aneurism; 2. The depth of the parts, and tendency of the intestines to roll into the wound; 3. Specially on the right side, the proximity of the great veins. With these exceptions the passing of the ligature is not so difficult as in some situations, the lax cellular tissue in which the vessel lies generally yielding much more easily than the tough sheath which elsewhere, as in the femoral, requires accurate dissection.

Incision.—(Plate I. fig. 3.)—From a point about half an inch above the centre of Poupart's ligament, a crescentic incision should be made, at first extending upwards and outwards, so as to pass about one inch inside of the anterior superior spine of the ilium, and then prolonged upwards and inwards, as far as may be rendered necessary by the size of the aneurism or the depth of parts. It must extend through skin and superficial fascia, exposing the tendon of the external oblique, which must then be slit up to the full extent visible. The