This artery has been tied for aneurism affecting one of its large branches on the back of the pelvis — the gluteal or sciatic.

It is arrived at by dividing the abdominal muscles before the iliac fossa to a greater extent than is required for exposing the external iliac — in the manner of the operation first mentioned for the common iliac. The vein, a large one is, it will be borne in mind, behind the artery and in contact with it : it is occasionally double. There is some difference in the degree of difficulty that would be experienced in securing the internal iliac artery in different cases. This is owing to the fact that, when short, (and, as shown above, it often is so,) the artery is placed deeply in the pelvis; whereas, when the length is more considerable, it is accessible above that cavity. Again, when the artery is very short, it would probably be more safe to tie the common iliac, or both the external and the internal iliacs at their origin than to place a ligature on the latter only, close to a strong current of blood. The internal iliac artery in thefatus (hypogastric), curves forwards from the common iliac artery to the side of the urinary bladder. In this course it descends but little, as the bladder projects into the abdomen in early life. Coursing upwards by the side and fundus of that organ, the vessel reaches the anterior wall of the abdomen, along which it ascends towards the umbilicus, converging to the vessel of the opposite side. At the umbilicus the two arteries come into contact with the umbilical vein, and then escaping with that vein from the abdomen, coil round it in the umbilical cord, and ramify in the substance of the placenta. To that part of the vessel which is placed within the abdomen, the term hypogastric is applied ; the remaining portion thence onward through the umbilicus to the placenta, being the proper umbilical artery. In the first part of its course each vessel lies along the margin and side of the pelvis, covered by the peritoneum and crossed by the ureter; it next lies between that membrane and the side of the bladder, to which it gives branches (superior vesical), and is crossed in the male by the vas deferens; and finally, it ascends towards the umbilicus, between the peritoneum and the fascia trans- versalis, the latter separating it from the rectus muscle and its sheath. After the cessation of the placental circulation at birth, the two hypogastric arteries become impervious from the side of the bladder upwards to the umbilicus, and are converted into fibrous cords. These two cords, which extend from the sides of the bladder to behind the umbilicus, being shorter than the sac of the peritoneum on which they rest, cause the serous membrane to project inwards, and thus are formed two fossce (fossa? of the peritoneum) on each side of the abdomen. The part of the artery intervening between the origin of the vessel and the side of the bladder, still continues pervious, and though reduced proportionately in size, continues to convey blood to the bladder, constituting the superior vesical artery. Branches. — The branches of the internal iliac artery, though conslant and regular in their existence and general distribution, vary much in their origin. Some are distributed to the parts or organs within the pelvis, viz., to the rectum, the urinary bladder, the spinal canal, and the organs peculiar to the female; whilst others of larger size supply chiefly the muscles upon the outer side of the pelvis. The branches furnished to these several structures will, in most cases, be observed to arise from two principal divisions of the parent trunk, of which one is anterior to the other. From the anterior division the following branches usually arise, viz., the superior vesical (the pervious portion of the foetal hypogastric artery), the inferior vesical, middle haemorrhoidal, obturator, internal pudic, and sciatic arteries, with (in the female) the uterine and the vaginal. The posterior division gives off the gluteal, the ilio-lumbar and the lateral sacral arteries. Sometimes all the branches of the internal iliac artery arise without the previous separation of that vessel into two divisions. In more than a fourth of a large number of cases noted, a branch arose before the subdivision of the main trunk. This branch was usually the ilio-lumbar artery Internal iliac artery.

From Quain's anatomy.