THE ABDOMINAL AORTA 255 



on either side from the renal artery, and passing antero- 

 laterad to the body-wall, supplying also the suprarenal 

 body. 



Occasionally the suprarenal artery originates separately, either 

 from the renal artery or from the aorta itself. 



(c) The lumbar arteries (aa. lumbales), seven pairs of vessels 

 distributed metamerically to the lumbar portion of the 

 body-wall. Six pairs arise from the dorsal wall of the aorta, 

 the seventh from the median sacral artery, each pair 

 originating as a single trunk which branches to right and left. 



(d) The median sacral artery (a. sacralis media) arises from 

 the dorsal wall of the aorta near its posterior end, and 

 passes backward on the ventral surface of the sacrum and 

 of the caudal vertebrae in the middle line. Its first portion 

 is concealed from the ventral surface by the common 

 hypogastric vein. 



2. The common iliac artery (a. iliaca communis) is a short paired 

 trunk, the branches of which pass to the posterior limb, the 

 wall of the pelvis, and the pelvic viscera. The first branch 

 is usually the iliolumbar artery, which passes laterad to the 

 body wall, though the point of origin of this vessel varies 

 considerably and may be on the aorta itself. After giving off 

 the iliolumbar artery, the common iliac divides into two 

 branches, the external iliac and the hypogastric. The con- 

 nections of these may be traced as follows: 



(a) The external iliac artery (a. iliaca externa) is the larger, 

 lateral branch, directed toward the inguinal ligament, over 

 which it passes to the medial surface of the limb, becoming 

 the femoral artery. Near its crossing with the ligament it 

 gives off the inferior epigastric artery (a. epigastrica 

 inferior), the main portion of which passes forward in the 

 medial portion of the abdominal wall. 



(b) The hypogastric artery (a. hypogastrica formerly known 

 also as internal iliac artery^ is the smaller, medial branch, 

 directed backward on the dorsal wall of the pelvis. Its 

 course may be traced, care being taken not to injure the 

 nerves of the lumbosacral plexus. Where it diverges from 



