COMMON ILIAC. 



429 



on the inner side, and partly beneath the artery ; on its outer side, it is in relation 

 with the Psoas magnus. 



Branches. The common iliac arteries give off small branches to the peritoneum, 

 Psose muscles, ureters, and to the surrounding cellular membrane, and occasionally 

 give origin to the ilio-lumbar, or renal arteries. 



Peculiarities. Its point of origin varies according to the bifurcation of the aorta. In three- 

 fourths of a large number of cases, the aorta bifurcated either upon the fourth lumbar vertebra, 

 or upon the intervertebral disk between it and the fifth ; one case in nine being below, and one in 

 eleven above this point. In ten out of every thirteen cases, the vessel bifurcated within half an 

 inch above or below the level of the crest of the ilium ; more frequently below than above. 



The point of division is subject to great variety. In two-thirds of a large number of cases, it 

 was between the last lumbar vertebra and the upper border of the sacrum; in one case in eight 

 being above, and in one in six below that point. The left common iliac artery divides lower 

 down more frequently than the right. 



The relative length, also, of the two common iliac arteries varies. The right common iliac 

 was longest in sixty-three cases ; the left, in fifty-two ; whilst they were both equal in fifty-three. 

 The length of the arteries varied in five-sevenths of the cases examined, from an inch and a half 

 to three inches ; in about half of the remaining cases, the artery was longer ; and in the other 

 half, shorter ; the minimum length being less than half an inch, the maximum four and a half 

 inches. In one instance, the right common iliac was found wanting, the external and internal 

 iliacs arising directly from the aorta. 



Fig. 227. Arteries of the Pelvis. 



Surgical Anatomy. The application of a ligature to the common iliac artery may be required 

 on account of aneurism or hemorrhage, implicating the external or internal iliacs, or on account 



