ABDOMINAL CAVITY 395 



the original continuation, passes downwards and backwards 

 into the pelvis minor. 



The common iliac artery of each side is covered by 

 peritoneum, and overlapped by coils of the small intestine ; 

 furthermore, it is crossed by the large sympathetic twigs 

 which connect the aortic and hypogastric plexuses, and, close 

 to its termination, by the ureter. On the left side the superior 

 haemorrhoidal vessels also pass in front of the common iliac 

 artery medial to the ureter. 



The left common iliac artery is in relation posteriorly with 

 the bodies of the last two lumbar vertebrae, the left sympa- 

 thetic trunk and the medial margin of the left psoas major 

 muscle. The right artery is separated from the vertebrae and 

 the sympathetic trunk by the two common iliac veins and 

 the commencement of the inferior vena cava. 



No collateral branches of any consequence proceed from 

 the common iliac arteries. 



Vense Iliacse Communes. Each of the two common iliac 

 veins is formed by the junction of the external iliac and 

 hypogastric veins of the corresponding side, the junction 

 taking place behind the upper end of the hypogastric artery. 

 The left common iliac vein is much longer than the right, and 

 stands in relation to both common iliac arteries. It first 

 lies along the medial or right side of its companion artery, and 

 on a posterior plane ; then it passes behind the upper part 

 of the right artery to reach the vena cava inferior. The 

 right common iliac vein lies behind its companion artery, 

 and behind the upper part of the artery it joins with the left 

 vein to form the inferior vena cava. 



Tributaries. In addition to the external iliac and hypo- 

 gastric veins, by the union of which it is formed, the common 

 iliac vein of each side is joined by an ilio-lumbar vein. The 

 left common iliac vein receives, in addition, the middle sacral 

 vein. 



Arterise Iliacae Externse. Each external iliac artery is the 

 first or abdominal portion of the great arterial trunk which 

 carries blood to the lower limb. It begins opposite the 

 corresponding sacro-iliac articulation, at the level of the lumbo- 

 sacral articulation, and extends obliquely downwards and 

 laterally, along the brim of the pelvis minor, to the inguinal 

 ligament, behind which it passes into the thigh, and becomes 

 the femoral artery. Its course is indicated on the surface by 



