[Fig. 126].—Abdominal Blood-vessels, Ventral View.

a, vena cava inferior; b, abdominal aorta; c, A. cœliaca (cut); d, A. mesenterica superior (cut); e, A. adrenolumbalis; f, A. phrenica; g, A. renalis; h, A. spermatica interna; i, A. mesenterica inferior (cut); j, A. iliolumbalis; k, A. iliaca externa; l, A. hypogastrica; m, beginning of A. femoralis; n, A. umbilicalis; o, A. and V. sacralis media (o, the artery; o′, the vein); p, A. glutea superior; q, A. glutea inferior; r, A. and V. hemorrhoidalis media; s, V. adrenolumbalis; t, V. renalis; u, V. spermatica interna; v, V. iliolumbalis; w, V. iliaca communis; x, V. femoralis; y, V. and A. profunda femoris; z, V. hypogastrica. 1, suprarenal body; 2, kidney; 3, ureter; 4, outline (broken) of rectum.

5. A. spermatica interna (h).—This rises from the aorta on each side at about the level of the caudal ends of the kidneys, and passes laterad (or it may arise from the renal). In male specimens the artery turns caudad, along with the corresponding vein (u), and passes to the inguinal canal. Thence it passes along with the vas deferens and the vein (forming all together the spermatic cord) to the testes and the other structures in the scrotum.

In females ([Fig. 112], 2, [page 265]) the artery is larger and passes more nearly directly laterad, being much convoluted. It passes to the ovary, being now called the ovarian artery. It sends branches into the ovary (c) and to the cranial end of the uterus (f); the latter anastomosing with branches of the uterine artery (3).

6. A. mesenterica inferior ([Fig. 126], i).—The inferior mesenteric artery has its origin from the aorta at about the level of the last lumbar vertebra. It passes toward the large intestine, and near it divides into two branches, the colica sinistra, which passes craniad along the descending colon, anastomosing with the colica media, and the superior hemorrhoidal, which passes caudad along the descending colon and rectum and anastomoses with the middle hemorrhoidal ([page 308]).

7. A. iliolumbalis ([Fig. 126], j).—The iliolumbar arteries arise from the aorta about two centimeters caudad of the inferior mesenteric and pass laterad over the ventral surface of the psoas minor and iliopsoas muscles. Each divides into two main branches, one passing caudad and the other craniad; these supply the muscles of this region. The cranial branch anastomoses with branches of the adrenolumbalis (e). The caudal branch sends an artery through the abdominal wall to appear at the cranial edge of the thigh; it passes onto the lateral surface of M. sartorius and extends here some distance distad.

8. A. lumbalis.—There are usually seven pairs of lumbar arteries, passing almost directly dorsad from the dorsal surface of the aorta; the first pair arising just craniad of the diaphragm, the last at the same level as the origin of the external iliac. The two arteries of a pair usually arise from the aorta one behind the other, or they may arise by a common trunk. They correspond to the intercostal arteries. They pass between the centra of the vertebræ and the muscles of the dorsal region, and send one main branch laterad, the other dorsad; both supply the dorsal muscles. From the dorsal branch small arteries pass into the vertebral canal to join the anterior spinal artery.

9. A. iliaca externa ([Fig. 126], k).—The external iliac artery passes obliquely caudad from the aorta, lying ventrad of the common iliac vein and against the medial surface of the psoas minor muscle. It passes onto the ventral surface of this and the iliopsoas and at the same time reaches the tendon of the abdominal muscles; through a small opening in this tendon lying ventrocaudad of that for the iliopsoas, it leaves the abdominal cavity. On its emergence from the abdominal cavity onto the medial surface of the thigh it receives the name A. femoralis (m). The branches of the external iliac artery are described below ([page 309]).

10. A. hypogastrica (or iliaca interna) ([Fig. 126], l).—The hypogastric or internal iliac arteries are given off from the aorta usually within a centimeter caudad of the external iliac. Each passes caudolaterad, lying on the medial side of the common iliac vein, and divides into branches which supply the structures within the pelvis and the muscles about the pelvic wall. There is much variation in the origin and relations of the branches of this artery. The following seems to be a very common arrangement: A very short distance from the origin the umbilical artery (n) is given off. The hypogastric artery then extends two or three centimeters and gives off A. glutea superior (p), which passes at once to the pelvic wall. A little farther caudad the hypogastric divides into the middle hemorrhoidal (r), to the rectum, and the glutea inferior (q), which passes out of the pelvis.