The branches of the external iliac artery serving of particular attention are usually two, the anterior or circumflex iliac and the tric arteries; throughout the superior part of its course the artery gives only minute branches to the peritoneum, the cellular tissue, the psom muscles, and the lymphatics; the other two, which have been mentioned, are given off mediately before the artery escapes from the abdomen. They arise at a very short distance above the erural arch, sometimes so high as three-fourths of an inch from it, at others at it, and sometimes again below the arch from the femoral ; they proceed one from the outer and the other from the inner side of the vessel sometimes opposite to each other, at others , differently one above the other ; occasionally they arc given off from a trunk common to both; they are nearly of equal size, but for the most part the epigastric is larger than the cir cumflex.
1. The anterior or circumflex iliac artery, (arteria cireumflexa ilium or ilii; Fr. artcre eirconflexe iliaque, ou iliaque ou antericure,) arises from the outer side of the external iliac on a level with or somewhat lower than the epigastric; it runs outward and upward above and parallel to the crural arch as far as the superior anterior spinous process of the ilium; during this course it lies upon the fascia iliaca superficial to the psoas and iliacus mus cies and the anterior erural nerve, and it is inclosed in a triangular canal, formed behind by the fascia iliaca, below and above by la minw of the fascia transversalis, which divides at its union with the former, in order to inclose the artery. When the anterior abdominal wall has been thrown down, and the peritoneum with the fascia propria removed from the iliac fossa, the course of the vessel may be traced by a white line, which marks the union of the two fascia:, extending from the middle of the crural arch upward and outward within about three fourths of an inch of the spinous process of the ilium ; by the division of the fascia trans versalis along this line the artery will be ex posed.
During its course toward the spinous process the artery gives branches to the psoas and iliacus, the transversalis and oblique muscles,. and to the inguinal glands ; near the process it gives upward a considerable branch, which ascends in the anterior wall of the abdomen, between the internal oblique and transversalis muscles, in front of the spinous process, serving with its accompanying veins as a guide in dis section by which to distinguish between the two muscles ; it divides into branches, which are distributed to the muscles, as also to the structures, which cover and line them, and communicate with branches of the epigastric,. lumbar, and intercostal arteries.
The circumflex artery pursues its course and runs backward around and within tire crest of the ilium, internal to the transversalis muscle ; during its course it gives branches inward to the iliacus muscle which anastomose with si milar branches from the iliolumbar, and up ward to the lateral abdominal muscles, which are partly distributed to them, partly turn over the crest of the ilium and communicate with the gluteal artery, and in part communicate with the lumbar or intercostal arteries. Finally,
the artery, very much reduced in size, anasto moses freely with the termination of the ilio lumbar, which pursues a similar course in a contrary direction around the interior of the crest of the ilium.
The circumflex artery has been found by Monro to present an irregularity deserving of notice; he has seen a branch from it, nearly as large as the epigastric, pass under the crural arch, about two inches from the symphysis pubis, and there divide into branches, which were distributed upon the symphysis and the fat and skin over the arch.
2. The epigastric artery, (Fr. artery epigas tripe, A. sus-pubienne) arises from the in ternal and rather anterior part of tire iliac artery, near to the crural arch ; the distance of its origin from the arch, however, is liable to variety ; for the most part it occurs about half an inch above it, but it is frequently nearer to it, or even at it, and occasionally it is below it, arising from the femoral artery; it is given off, as has been stated, from that part of the iliac, which is left uncovered by peri toneum, and its point of origin is posterior to, sometimes above, sometimes on a level with, and at others below the reflection of the mem !wane from the posterior to the anterior wall of the abdomen. Its course is tortuous ; it passes forward and inward ; when its origin is low, or very near to the arch, at once upward ; but when its origin is high, at first downward in front of the external iliac vein, and then changing its direction, when it has reached the reflection of the peritoneum, it ascends inward toward the outer margin of the rectos muscle, in front of the membrane, between it and the fascia transversalis ; it reaches the margin of the muscle from one and a half to two inches above the pubis, and then passing behind it enters its sheath, and continues its course upon the posterior surface of the muscle toward the umbilicus, and terminates by dividing into branches, which anastomose freely with de scending branches of the internal mammary artery ; the main course of the vessel is there fore oblique upward and inward ; and it may be defined by a line drawn from the junction of the middle and inner third of the crural arch to within half an inch upon either side of the umbilicus.