516 ARTERIES. 



ponding posterior sacral foramen, supplies the skin and muscles on the dorsum 

 of the sacrum. 



The inferior branch passes obliquely across the front of the Pyriformis muscle 

 and sacral nerves to the inner side of the anterior sacral foramina, descends on 

 the front of the sacrum, and anastomoses over the coccyx with the sacra media 

 and opposite lateral sacral arteries. In its course, it gives off branches, which 

 enter the anterior sacral foramina : these, after supplying the bones and mem- 

 branes of the interior of the spinal canal, escape by the posterior sacral fora- 

 mina, and are distributed to the muscles and skin on the dorsal surface of the 

 sacrum. 



EXTERNAL ILIAC ARTERY. (Fig. 294.) 



The External Iliac Artery is the chief vessel which supplies the lower limb. 

 It is larger in the adult than the internal iliac, and passes obliquely downwards 

 and outwards along the inner border of the Psoas muscle, from the bifurcation 

 of the common iliac to the femoral arch, where it enters the thigh, and becomes 

 the femoral artery. The course of this vessel would be indicated by a line 

 drawn from the left side of the umbilicus to a point midway between the ante- 

 rior superior spinous process of the ilium and the symphysis pubis. 



Relations. In front, with the peritoneum, subperitoneal areolar tissue, the 

 intestines, and a thin layer of fascia, derived from the iliac fascia, which sur- 

 rounds the artery and vein. At its origin it is occasionally crossed by the 

 ureter. The spermatic vessels descend for some distance upon it near its 

 termination, and it is crossed in this situation by a branch of the genito-crural 

 nerve and the circumflex iliac vein ; the vas deferens curves down along its 

 inner side. Behind, it is in relation with the external iliac vein, which, at the 

 femoral arch, lies at its inner side ; on the left side the vein is altogether inter- 

 nal to the artery. Externally, it rests against the Psoas muscle, from which it 

 is separated by the iliac fascia. The artery rests upon this muscle near Pou- 

 part's ligament. Numerous lymphatic vessels and glands are found lying on 

 the front and inner side of the vessel. 



PLAN OF THE RELATIONS OF THE EXTERNAL ILIAC ARTERY. 



In front. 



Peritoneum, intestines, and iliac fascia. 

 Near f Spermatic vessels. 

 Pounirt's J Genit - crura l nerve. 

 Ligamen. Circumflex iliac vein 



^ Lymphatic vessels and glands. 



Outer side. I \ Inner side. 



Psoas Magnus. E mao. al External iliac vein and vas deferens 



Iliac fascia. V / at femoral arch. 



Behind. 



External iliac vein. 

 Psoas Magnus. 



Surgical Anatomy. The application of a ligature to the g external iliac may be required in 

 cases of aneurism of the femoral artery, or in cases of secondary hemorrhage, after the latter 

 vessel has been tied for popliteal aneurism. This vessel may be secured in any part of its 

 course, excepting near its upper end, which is to be avoided on account of the proximity of the 

 great stream of blood in the internal iliac, and near its lower end, which should also be avoided, 

 on account of the proximity of the epigastric and circumflex iliac vessels. One of the chief 

 points in the performance of the operation is to secure the vessel without injury to the perito- 

 neum. The patient having been placed in the recumbent position, an incision should be made, 

 commencing below at a point about three-quarters of an inch above Poupart's ligament, and a 

 little external to its centre, and running upwards and outwards, parallel to Poupart's ligament, 

 to a point above the anterior superior spine of the ilium. When the artery is deeply seated, 



