PET Mia 
ARTERIES OF THE LOWER EXTREMITY. 811 
back of the lower part of the sacrum and of the coccyx. It gives several branches to the 
gluteus maximus, and anastomoses with branches of the eluteal and lateral sacral arteries. 
(c) An anastomotic branch passes transversely outwards, over or under the great 
sciatic nerve, towards the great trochanter of the femur. It anastomoses with branches 
of the gluteal, pudic, internal and external circumflex x, and the first perforating arteries, 
taking part in the formation of the so-called ‘crucial anastomosis.”  (d) Gnianeoue 
branches, accompanying twigs of the small sciatic nerve, pass round the lower border 
of the gluteus maximus muscle to the integument. (e) The comes nervi ischiatici (a. 
comitans n. ischiadici) is a long slender branch which runs down on the surface, or in 
the substance of the great sciatic nerve. It supplies the nerve, and anastomoses with the 
perforating arteries anid with the termination of the profunda. 
ARTERIES OF THE LOWER EXTREMITY. 
The main artery of each lower limb is continued from the corresponding com- 
mon iliac artery. It descends as a single trunk as far as the lower border of the 
pophteus, and ends there by dividing into the anterior and posterior tibial arteries. 
Distinctive names are, however, applied to different parts of the artery, correspond- 
ing to the several regions through which it passes. Thus in the abdomen it is 
called the external iliac artery, in the upper two-thirds of the thigh it receives the 
name of the femoral artery, whilst its lower part, which is situated on the flexor 
aspect of the knee, is termed the popliteal artery. 
THE EXTERNAL ILIAC ARTERY. 
The external iliac artery (a. iliaca externa) extends from the level of the lumbo- 
sacral articulation to a point beneath Poupart’s Hgament, midway between the 
anterior superior spine of the ileum and the symphysis pubis, where it becomes the 
femoral artery. Its length is about three and a half inches (87 to 100 mm.), and 
in the adult it is usually somewhat larger than the internal iliac artery. 
It runs downwards, outwards, and forwards along the brim of the pelvis, rest- 
ing upon the iliac fascia, which separates it above from the imner_ border, and 
below from the anterior surface of the psoas muscle, and it is enclosed with its 
accompanying vein in a thin fascial sheath. 
Relations.— dnterior—_It is covered in front by peritoneum, which separates it on 
the right side from the pelvic colon, iliac colon, and coils of small intestine, and on the right 
side from the terminal portion of the ileum, and sometimes from the vermiform appendix. 
The ureter, descending behind the peritoneum, § sometimes crosses the front of the artery 
near its origin, and in the female the ovarian vessels cross the upper part of the artery. 
Near its lower end the artery is crossed anteriorly by the genital branch of the genito- 
crural nerve and by the deep circumflex iliac vein. In the male this part of the artery is 
also crossed by the vas deferens, and in the female by the round ligament of the uterus. 
Several iliac lymphatic ¢ elands lie in front of the external iliac artery, and almost invari- 
ably one of these is dir ectly i in front of its termination. 
“Posterior.—The iliac fascia and psoas muscle lie behind the artery. Near its upper 
end the obturator nerve is also posterior to the vessel. 
Lateral,— Externally is the genito-crural nerve ; internally, and on a somewhat posterior 
plane, is the external iliac vein. 
Branches.—In addition to small branches to the psoas muscle and to the 
lymphatic glands, two named branches of considerable size spring from the external 
iliac artery, viz. the deep epigastric and the deep circumflex iliac. 
(1) The deep epigastric artery (a. epigastrica inferior, Figs. 569 and 572) arises 
immediately above Poupart’s ligament from the front of the external iliac. Cur ving 
forward from its origin it lies in the extra -peritoneal fat, turns round the lower 
border of the peritoneal sac, and runs upwards and inwards alc mg the inner side of 
the internal abdominal ring and along the outer border of Hesselbach’s triangle ; 
then pierces the transversalis fascia, passes over the semilunar fold of Douglas He 
enters the sheath of the rectus abdominis. For a short distance it ascends behind 
the rectus, but it soon penetrates the substance of the muscle, and breaks up into 
