THE COMMON ILIAC ARTERIES. 471 



Varieties. The place of division of these arteries is subject to great variety. In two- 

 thirds of a large number of cases it ranged between the middle of the last lumbar vertebra 

 and the upper margin of the sacrum, in one case in eight it was above, and in one case in 

 six it was below that space. Most frequently the left artery was found to divide lower than 

 the right (R. Quain). 



The length varies in most instances between an inch and a half and three inches, but it 

 has been seen in some rare cases less than half an inch, and as long as four inches and a half. 

 When longer than usual the artery is generally more or less tortuous. In two instances 

 absence of one common iliac artery has been observed, the internal and external iliacs of 

 that side springing directly from the end of the aorta (on the right side by Cruveilhier, on the 

 left side by W. J. Walsham). 



Branches. The common iliac artery occasionally gives off the middle sacral ,Tihe~ilio-lumbar, 

 or the upper lateral sacral artery, more rarely a lumbar, an accessory renal, or a spermatic artery, 



SURGICAL ANATOMY OF THE COMMON ILIAC ARTERY. 



The common iliac artery may be reached in an operation by dividing the abdominal muscles 

 in the lumbar region. A semilunar incision, having its convexity turned outwards, may be 

 carried from a point an inch and a half to the inner side of the anterior superior iliac spine, 

 upwards and somewhat outwards, to near the lower margin of the thorax. The external 

 oblique, internal oblique, and transversalis muscles are successively divided, together with the 

 thin transversalis fascia ; the peritoneum, to which the ureter and speimatic vessels adhere 

 closely, is next separated from the lateral abdominal wall and the surface of the psoas until 

 the artery is reached ; the areolar sheath is then scraped through and the ligature applied, the 

 needle being passed on either side from right to left. It seldom happens that the common 

 iliac artery is too short to allow of the application of a ligature, but if it were found to be 

 less than an inch and a half in length, the external and internal iliac trunks might be 

 secured close to the bifurcation. 



Collateral circulation. After ligature of the common iliac artery, blood is conveyed to 

 the external iliac trunk through the anastomoses of the circumflex iliac with the lumbar 

 arteries, and of the epigastric with the internal mammary ; to the internal iliac through the 

 anastomoses of the middle with the lateral sacral arteries, of the lumbar with the ilio-lumbar, 

 of the superior with the middle and inferior hsemorrhoidal, and of the obturator and the 

 arteries supplied to the pelvic viscera with the corresponding vessels of the opposite side. 



INTERNAL ILIAC ARTERY (II). 



The internal iliac artery (hypogastric) extends from the bifurcation of the 

 common iliac artery downwards towards the great sacro-sciatic foramen, near the 

 upper border of which it divides into branches. It is generally from an inch to an 

 inch and a half in length, and is smaller than the external iliac in the adult, but the 

 reverse in the foetus. At its origin, the artery lies near the inner border of the 

 psoas muscle ; lower down, it rests against the sacrum and lumbo-sacral nervous 

 cord. It is covered by the layer of peritoneum constituting the posterior false 

 ligament of the bladder, and beneath this the ureter crosses it on the inner side. 

 The companion vein lies behind, and somewhat to its inner side, and the commence- 

 ment of the artery crosses the upper end of the external iliac vein. 



BRANCHES. The branches of the internal iliac artery, though constant and 

 regular in their general distribution, vary much in their mode of origin. They 

 arise, in most instances, from two principal divisions of the parent trunk, of which 

 one is anterior to the other. From the anterior division arise the superior vesical 

 (connected with the pervious portion of the foetal hypogastric artery), the inferior 

 vesical (vaginal in the female), middle haemorrhoidal, obturator, internal pudic, and 

 sciatic arteries, and also, in the female, the uterine artery. The posterior division 

 gives off the ilio-lumbar and lateral sacral arteries, and is continued into the gluteal. 



Varieties. Length. The internal iliac artery has been found as short as half an inch, 

 and sometimes as long as three inches, but it is not often less than an inch in length. Three 

 instances are recorded in which this vessel was absent on the left side, and its branches were 

 derived from a loop of the external iliac artery dipping down into the pelvis (Ellis, Eckhard, 



