776 A MANUAL OF ANATOMY 



vein, which, from below upwards, lies first on its inner side, then 

 behind it, and finally on its outer side. 



Branches. — ^These are as follows : peritoneal to the peritoneum 

 and subperitoneal areolar tissue ; muscular to the psoas magnus ; 

 ureteric to the ureter (all of small size and unimportant) ; external 

 iliac ; and internal iliac. In some cases the common iliac gives of^ 

 one or other of the following vessels : ilio-lumbar, middle sacral, 

 lateral sacral, lumbar, or an aberrant renal artery. 



Varieties. — The chief variety affects the length of the vessel. It may be 

 very short, which is due either to a low bifurcation of the aorta or a high 

 bifurcation of the artery itself ; or it may be very long, which is due to exactly 

 opposite causes. When abnormally long, the vessel is usually more or less 

 tortuous. 



Collateral Circulation. — After ligature of a common iliac artery, the chief 

 channels by which the circulation is carried on are as follows : ( i ) the superior 

 epigastric of the internal mammary from the first part of the subclavian anasto- 

 moses with the deep epigastric of the external iUac ; (2) the lumbar branches 

 of the aorta anastomose with (a) the lateral or intermuscular epigastric of the 

 deep circumflex iliac from th^-eKternal iliac, and (b) the ilio-lumbar of the 

 internal iliac ; (3) the superior hemorrhoidal of the inferior mesenteric from 

 the aorta anastomoses with (a) the middle hemorrhoidal of the internal iliac, 

 and (b) the inferior hemorrhoidal of the internal pudic from the internal iliac ; 

 (4) the middle sacral from the aorta anastomoses with the lateral sacral branches 

 of the internal iliac ; and (5) the pubic branches of the obturator from the 

 internal iliac and of the deep epigastric from the external iliac, both of one 

 side, anastomose across the middle line with the corresponding branches of 

 the opposite side. The vesical, and middle and inferior hemorrhoidal arteries 

 of one side anastomose in a similar manner with those of the opposite 

 side. 



Common Iliac Veins. — Each vein is formed by the union of the 

 external and internal iliac veins opposite the corresponding sacro- 

 iliac articulation, on a level with the brim of the pelvis. They 

 unite to form the inferior vena cava opposite the upper border of 

 the body of the fifth lumbar vertebra a little to the right of the 

 middle line, behind and on the right side of the right common iliac 

 artery. The right vein is necessarily shorter than the left, and it 

 ascends almost vertically, lying at first internal to, then behind, 

 and finally on the outer side of its own artery. The left vein ascends 

 very obliquely from left to right, lying internal to its own artery, 

 and then behind that of the right side. It crosses the middle sacral 

 artery, and is crossed by the superior hemorrhoidal vessels and the 

 left half of the aortic plexus. The common iliac veins are usually 

 destitute of valves. 



Tributaries. — These are chiefly the external iliac, internal iliac, 

 and ilio-lumbar. In addition, the left vein receives the middle 

 sacral vein. 



The left common iliac vein is mainly the persistent and enlarged transverse 

 branch (transverse iliac) which connects the right and left cardinal veins of 

 the embryo above the back part of the pelvic brim. Its commencement, 

 however, is developed from a portion of the left cardinal vein. The right 

 common iliac vein is developed from the part of the right cardinal vein which 

 intervenes between the termination of the right external iliac vein and the 

 right extremity of the transverse iliac vein. 



