TRE EXTERNAL ILIAC ABTEBIE8. 545 



iscliiaiic branch in Solipeda ; it escapes from tlie pelvic cavity witli the ^reat sciatic 

 nerve, whicli it accompanies to beliiud the thigh, where it is expended, after giving off 

 on its course spinal and gluteal twigs. It is not this branch which supplies ) he coccy- 

 geal arteries ; these come, as in the Pig and Ruminants, from the middle sacral artery. 



COMPAEISON OP THE INTEIiNAL ILIAC AKTEUIES IN MAN WITH THOSE OP ANIMALS. 



The aorta in Man bifurcates at the fourth lumbar vertebra to form the primitive (or 

 common) iliac arteries, which descend to each side of the margin of the pelvis, where 

 they divide into two branches, the internal and external iliacs. 



The internal iliac, or hypogastric artery, passis beneath the sacro-iliac articulation, 

 and breaks up into nine or eleven branches that go to the walls of the pelvic cavity, or 

 to the organs contained in it. Their disposilion somewhat resembles that of Car- 

 nivora ; in their distribution they represent the various branches of the internal iliac of 

 Solipeds. Thus we find : 1, An umbilical artery ; 2, The vesico-prostatic artery, re- 

 sembling the branch of the same name given off in the Horse by the internal pudic ; 

 3, The middle hsemorrlioidal artery, that passes to the rectum like the branch of the 

 internal pudic ; 4, The iUo-lumbar artery, the iliaco-muscular of Solipeds ; 5, The lateral 

 sacral artery, which, behind, joins the middle sacral instead of dividing, as in the Horse, 

 into ischiatic and lateral coccygeal ; 6, Tlie obturator artery ; 7, Gluteal artery ; 8, 7s- 

 chiatic ; 9, Internal pudic, that terminates, as in animals, by the cavernous, diirsalis 

 penis, and the transversa perinei arteries. Tlie arterial branches of the rectum, or 

 inferior hsemorrhoidal, are furnished by the internal pudic aitery. 



Aktiole IV. — External iLiAO Arteries or Cetjral Trunks. (Fig. 277, 11.) 



The external branches of the terminal quadrifurcations of the posterior 

 aorta, the crural trunks descend on the sides of the entrance to the pelvic 

 cavity, in describing a curve downwards and forwards, and a direction 

 oblique from above to below, before to behind, and within outwards. 

 Maintained within the small psoas and iliacus muscles by the peritoneum 

 covering them, they are bordered posteriorly, ard to the inner side, by 

 the iliac vein, which isolates them from the pelvic trunk. When they 

 arrive at the anterior border of the pubis, in the interstice which separates 

 the pectineus from the long adductor of the leg, each is prolonged to 

 the thigh, and takes the name of femoral artery ; and thence into the angle 

 of the femoro-tibial articulation, where it receives the denomination of 

 popliteal artery. 



Before passing to the description of these two vessels — continuations 

 of the external iliac artery, we will indicate the collateral branches which 

 emanate from this trunk itself. These are two principal: the small 

 testicular or uterine (cremasteric), and the circimflexa Hit. The first having 

 been already described (p. 534), we have only to notice the second. 



Circumflex Iliac Artery (Fig. 272, 11).— This artery commences at 

 an acute angle near the origin, and in front of, the external iliac; it 

 sometimes emerges directly from the abdominal aorta. It is directed 

 outwards, passes between the peritoneum and the lumbo-iliac aponeurosis, 

 and arriving at the external border of the great psoas muscle, or even 

 beyond that, it bifurcates. The anterior branch sends its ramifications into 

 the transverse and small oblique muscles of the abdomen, where they 

 anastomose with the abdominal ramuscules of the lumbar and intercostal 

 branches; the posterior bifurcation, after giving some vessels to the same 

 muscles, traverses the abdominal wall a little below the external angle of the 

 ilium, in passing between the small oblique and iliacus muscles, to descend 

 •wfithin the anterior border of the ilio-aponeuroticus (tensor vaginee) muscle, 

 and expend itself in front of the thigh by subcutaneous divisions. 



