INTERNAL ILIAC. 509 



the lumbar region, and terminating a little below the anterior superior iliac spine. The abdominal 

 muscles (in either case) having bren cautiously divided in succession, the transversalis fascia 

 must be carefully cut through and the peritoneum, together with the ureter, separated from the 

 artery, and pushed aside ; the sacro-iliac articulation must then be felt for, and upon it the vessel 

 will be felt pulsating, and may be fully exposed in close connection with its accompanying 

 vein. On the right side, both common iliac veins, as well as the inferior vena cava, are in close 

 connection with the artery, and must be carefully avoided. On the left side, the vein usually 

 lies on the inner side, and behind the artery; but it occasionally happens that the two comnum 

 iliac veins are joined on the left instead of the right side, which would add much to the diffi- 

 culty of an operation in such a case. The common iliac artery may be so short that danger may 

 be apprehended from secondary hemorrhage if a ligature is applied to it. It would be prefer- 

 able, in such a case, to tie both the external and internal iliacs near their origin. 



Collateral Circulation. The principal agents in carrying on the collateral circulation after 

 the application of a ligature to the common iliac, are, the anastomoses of the haemorrhoidal 

 branches of the internal iliac, with the superior haemorrhoidal from the inferior mesenteric ; the 

 anastomoses of the uterine and ovarian arteries, and of the vesical arteries of opposite sides ; of 

 the lateral sacral, with the middle sacral artery ; of the epigastric, with the internal mammary, 

 inferior intercostal, and lumbar arteries ; of the ilio-lumbar, with the last lumbar artery ; of the 

 obturator artery, by means of its pubic branch, with the vessel of the opposite side, and with 

 the internal epigastric; and of the gluteal, with the posterior branches of the sacral arteries. 



INTERNAL ILIAC ARTERY. (Fig. 294.) 



The Internal Iliac Artery supplies the walls and viscera of the pelvis, the 

 generative organs, and inner side of the thigh. It is a short, thick vessel, 

 smaller than the external iliac, and about an inch and a half in length, which 

 arises at the point of bifurcation of the common iliac ; and, passing downwards 

 to the upper margin of the great sacro-sciatic foramen, divides into two large 

 trunks, an anterior and posterior ; a partially obliterated cord, the hypogastric 

 artery, extending from the extremity of the vessel forwards to the bladder. 



Relations. In front, with the ureter, which separates it from the peritoneum. 

 Behind, with the internal iliac vein, the lumbo-sacral nerve, and Pyriformis 

 muscle. By its outer side, near its origin with the Psoas muscle. 



PLAN OF THE EELATIONS OF THE INTERNAL ILIAC AETERY. 



In front. 

 Peritoneum. 

 Ureter. 



Outer side. 

 Psoas Magnus. 



Behind. 



Internal iliac vein. 

 Llimbo-sacral nerve. 

 Pyriformis muscle. 



In the foetus, the internal iliac artery (hypogastric) is twice as large as the 

 external iliac, and appears to be the continuation of the common iliac. Passing 

 forwards to the bladder, it ascends along the side of that viscus to its summit, 

 to which it gives branches ; it then passes upwards along the back part of the 

 anterior wall of the abdomen to the umbilicus, converging towards its fellow of 

 the opposite side. Having passed through the umbilical opening, the two ar. 

 teries twine round the umbilical vein, forming with it the umbilical cord ; and, 

 ultimately, ramify in the placenta. The portion of the vessel within the ab- 

 domen is called the hypogastric artery ; and that external to that cavity, the 

 umbilical artery. 



At birth,^ when the placental circulation ceases, that portion of the hypogastric 

 artery which extends from the umbilicus to the summit of the bladder, con- 

 tracts, and ultimately dwindles to a solid fibrous cord; the portion of the same 



