256 ANATOMY OF THE RABBIT 



external iliac the vessel gives off the umbilical artery 

 (a. umbilicalis) to the bladder, or in the female first to the 

 vagina and uterus (a. uterina). The next branch of the 

 hypogastric is the obturator artery, which passes postero- 

 laterad to the pelvic wall. About the same point arises the 

 medial femoral circumflex artery, which runs more directly 

 laterad into the muscles of the thigh. Slightly further back, 

 the hypogastric gives rise to the middle haemorrhoidal 

 artery to the side of the rectum and the urethra in the male 

 or to the rectum and the vestibulum in the female. The 

 hypogastric then leaves the pelvic cavity as the sciatic 

 artery (a. ischiadica), passing to the lateral side of the 

 abductor caudae anterior muscle. The sciatic artery re- 

 appears posteriorly, and divides into the internal pudendal 

 and lateral caudal arteries. 



3. The inferior caval vein (v. cava inferior) is formed on the 

 dorsal surface of the posterior end of the aorta by the union of 

 the paired external iliac veins with the common hypogastric, 

 the latter a short median trunk receiving the paired hypogastric 

 veins. From this position it passes to the right side of the aorta 

 (rarely to the left) almost to its ventral surface, and then runs 

 forward on the right side to the diaphragm. Its visceral roots 

 or tributaries (radices viscerales) comprise the paired renal 

 and spermatic veins, and the hepatic veins from the liver 

 (p. 234). Its parietal tributaries (radices parietales) include 

 the inferior phrenic veins (vv. phrenicae inferiores), which 

 enter the inferior cava from either side of the diaphragm, the 

 lumbar veins (vv. lumbales), a series of six pairs of vessels just 

 in front of the corresponding first six lumbar arteries, and the 

 paired iliolumbar vein (v. iliolumbalis). The members of each 

 of the first two pairs of lumbar veins unite to form a single 

 short trunk but the more posterior veins enter the vena cava 

 separately. The suprarenolumbar vein at each side joins the 

 renal vein or may enter the inferior vena cava directly. 



The paired hypogastric vein receives as its largest tributary 

 the sciatic vein from the back of the thigh. It also receives an 

 external haemorrhoidal vein and a small obturator vein and 



