So8 HUMAN ANATOMY. 



and both common iliac veins are in close relation w ith the artery, the latter two 

 passing beneath it. On the left side, the inferior mesenteric vessels as they enter 

 the sigmoid mesocolon and pass downward to the rectum cover practically the 

 whole of the artery, and to reach the common iliac comfortably and safely the 

 peritoneum would need to be divided close to the left of the median line of the 

 sacrum and be displaced outward. The vein usually lies on the inner side of 

 and somewhat behind the artery. This manoeuvre has the disadvantage of ex- 

 posing the vein freely, but this would probably give far less trouble than would the 

 numerous mesenteric vessels when swollen by reason of the loss of their peritoneal 

 support. 



2. By the extraperitoneal method the vessel is approached through various 

 incisions ; the best (Crampton) (especially if it is desirable to apply the ligature at 

 the highest possible point) begins at the tip of the last rib and extends downward to 

 the ilium and forward to the anterior superior spinous process. The abdominal 

 muscles and transversalis fascia are divided at the lower extremity of the wound, the 

 peritoneum separated with the finger from the iliac fascia in a direction corresponding 

 to the line of the crista ilii, the abdominal muscles severed on the same line, and the 

 separation of the peritoneum continued until it is pushed off the psoas and the iliac 

 vessels, which lie on the inner aspect of that muscle. The ureter is raised with the 

 peritoneum and remains attached to it. 



The artery may be similarly approached through an incision placed just above 

 Poupart's ligament and very like that used for the exposure of the external iliac. The 

 needle is passed from the vein — /. e. , from left to right — in ligating the right common 

 iliac, and from right to left if the vessel of the left side is the subject of operation. 



The collateral circulatio7i is carried on from above the ligature by (a) the inter- 

 nal mammary; (J)) the superior hemorrhoidal; {c) the lumbar; {d) the middle 

 sacral ; and (^) the pudic and obturator of the opposite side, anastomosing respect- 

 ively with (a) the deep epigastric ; (^b) the middle hemorrhoidal (internal iliac) ; (<:) 

 the deep circumflex iliac ; and (<?) the pudic and obturator of the other side (J.e.^ 

 the side of the ligature) from below. 



THE INTERNAL ILIAC ARTERY. 



The internal iliac artery (a. hypogastrica) (Fig. 724) arises from the common 

 iliac and passes almost directly downward in front of the sacro-iliac articulation into 

 the pelvis. Opposite the upper border of the great sacro-sciatic foramen it divides 

 into two main stems, the atiterior and posterior divisions, from which branches of 

 distribution are given off. 



Relations. — Posteriorly the internal iliac artery is covered by peritoneum and 

 is crossed obliquely by the ureter. More anteriorly the vessel of the right side is in 

 relation with some coils of the ileum, while that of the left side is in relation to the 

 upper part of the rectum. Posteriorly each artery rests upon the upper part of the 

 external iliac vein, which separates it from the inner border of the psoas muscle, and is 

 accompanied throughout its course by the internal iliac vein. 



Branches. — From the main stem of the artery, before its division, there arises 

 (i) the ilio-banbar 2iX\.^xy , and from its posterior division (2) the latej-al sacrals, 

 usually two in number, and (3) X\\q ghiteal. From the anterior division there are 

 given off a hypogastric axis, which divides into (4) the superior vesical, (5) inferior 

 vesical, and (6) prostatic or vaginal branches, and (7) the vesicido-deferential or 

 uterine artery, and, in addition, (8) the obturator and (9) middle hemorrhoidal 

 arteries, the main stem terminating by dividing into ( 10) the internal pudic and 

 (11) sciatic arteries. 



Variations. — The internal iliac arteries represent the proximal part of the fcetal umbilical 

 or hypog^astric arteries which return the blood from the frttus to the placenta. During intra- 

 uterme life these vessels are large and appear to be the continuation of the common iliacs, pass- 

 ing forward beneath the peritoneum to the lateral walls of the bladder and thence upward upon 

 the anterior abdominal wall to the umbilicus, and thence in the substance of the umbilical cord 

 to the placenta. After birth the arteries diminish in size, and those portions of them which pass 

 across the lateral walls of the urinary bladder and up the abdominal wall become converted into 

 solid fibrous cords which persist throughout life and are known as the obliterated hjrpogastric 



