THE VASCULAR SYSTEM 1 67 



the rigJit ovarian empties directly into the vena cava. A pair of 

 small iliolumbar veins collecting blood from the lumbar muscles 

 empty into the vena cava a centimeter or more craniad to the 

 large common iliacs. The union of the common iliac veins col- 

 lecting the blood from the hind-limbs and the pelvic region, and 

 the caudal vein, forms the beginning of the inferior vena cava. 

 The common iliac is formed by the union of the external and in- 

 ternal iliac veins in the pelvis. The former 

 is much the larger of the two. 



The portal system begins with the veins 

 collecting the blood from the intestines, 

 pancreas, spleen, and stomach, and termi- 

 nates where the hepatic veins enter the vena 

 cava. The inferior mesenteric vein collects 

 the blood from the large intestine ; the superior T^ 



mesenteric, from the small intestines; the gas- pj^, g _y ^ j ^ 

 trosplenic, from the spleen, stomach, and ^^^ Open. Arrow 



Shows the Direc- 



panereas; the coronary, from the lesser cur- tion of the Blood. 

 vature of the stomach; the gastro-epiploica, .^ "f fe^ edge "* if Thi 

 from the greater curvature of the stomach; valve, 

 and the pancreatoduodenalis , from the pan- 

 creas and duodenum. The last three may empty directly 

 into the portal vein or into one of the three branches first 

 named. Within the liver the blood is carried to the hepatic 

 lobules through the interlohiilar branches of the portal vein, from 

 which it is distributed to the intralobular sinusoids. It is 

 then collected by the central vein of the lobule and conveyed 

 through the hepatic veins to the postcava through which it reaches 

 the heart. 



The superior vena cava (precava) extends from the union of the 

 innominate veins to the right atrium. Three important 

 veins empty into the superior vena cava: the azygos, collecting 

 blood from the intercostal spaces; the sternal, lying on the vis- 

 ceral surface of the sternum; and the right vertebral, which, 

 with its fellow, collects the blood from the deep muscles and 



