The common iliac artery, extending in a line from the left side of the umbilicus towards the middle of Poupart's ligament, and being placed at its commencement on a level with the highest part of the crest of the ilium, may be approached in an operation, by dividing the abdominal muscles to a sufficient extent, in the iliac region and a little above this part of the abdomen.

The incisions might be made, beginning above Poupart's ligament, to the outer side of its middle, and running parallel with that structure towards the anterior superior spine of the iliac bone, thence curving for a couple of inches towards the umbilicus. In this way the artery will be approached from below ; but, if a tumour extends along the external iliac artery, this plan of operation would be objectionable, for the swelling itself, and, it may be, the adhesion of the peritoneum to its surface, would be sources of serious difficulty. Should the aneurism extend upwards in the abdomen it will be best to approach the artery from the side, or rather from above, — not from below. The essential part of the operation, so far as the abdominal muscles are concerned, is, that they should be divided to the extent of five or six inches at the side of the abdomen, beginning about two inches above the level of the umbilicus and ending lower than the spine of the ilium, the incision being curved outwards towards the lumbar region. Sir P. Crampton, in an operation to tie this artery, divided the muscles from the end of the lowest rib, straight down nearly to the crest of the ilium and thence forward a little above the border of the bone as far as its spine.* This plan is well devised for the object. The fascia behind the muscles (fascia transversalis) is to be cut through with care, and the peritoneum to be raised from that and the iliac fascia, as well as from the cellular membrane (sometimes containing a quantity of fat), which is interposed between the serous and the fibrous membranes. With the peritoneum will be raised the ureter, which adheres to it. The artery will be seen on the last lumbar vertebra ; and, on the right side of the body, large veins will be in view in close connexion with it, viz., both common iliac veins, and the commencement of the lower vena cava. It will be re- membered, that in some cases, (without transposition of the viscera, as well as with that condition,) the iliac veins are joined on the left instead of the right side; and that in another small class of cases the junction of those veins is delayed, so to say. The effect of either of these conformations of the venous system, would be to give to the artery on the left side much more than the usual complication with veins. Lastly, the thin cellular membrane covering the artery is divided without any difficulty to admit the passage of the ligature. The common iliac artery is in most cases of sufficient length to admit of the application of a ligature without much apprehension of secondary hemorrhage occurring in consequence of insufficiency in this respect. But it has been shown above to be in some instances very short — so short that the operation would be inadmissible. In any case in which the common trunk is thus short, it would probably be more prudent to place a ligature on the external iliac and another on the internal iliac, at the origin of each, than to tie the common iliac artery, or the external iliac alone near its commencement. The surgeon has it in his power to judge of the length of the artery during the operation, and to determine as to the propriety of tying one vessel or the other, for the iliac arteries are under his view almost as fully as if dissected. Arteries in other parts of the body, are, on the contrary, only seen at the point at which it has been beforehand determined to place the ligature. No branch that has received a name is given off by the common iliac arteries in their course ; but somewhat above the sacro-iliac symphysis, as has been observed, each divides into two branches, the in- ternal and external iliac arteries. Of these the internal iliac artery, which furnishes branches to supply the pelvis, pelvic viscera, and the perineum, will be first described. The common iliac artery, it should be added, often gives off a small unnamed branch to the lymphatic glands, the ureter or the psoas muscle, and sometimes even a larger branch — a renal artery or the ilio-lumbar.

From Quain's anatomy.