CLASS AMPHIBIA 509 



The large posterior vena cava originates between the kidneys and 

 receives blood from each kidney by five or six renal veins, from the 

 gonads by small spermatic or ovarian veins, and from the fat bodies 

 by other small branches. Near the heart the vena cava receives two 

 large hepatic veins from each side of the liver. 



The Hepatic Portal System. — This system is comprised of two 

 chief veins, the hepatic portal vein and the ventral abdominal vein. 

 These veins, instead of carrying blood directly to the heart, bring 

 it to the liver to pass through a netAvork of sinusoids (modified 

 capillaries). It is returned to the systemic system through hepatic 

 veins that join the postcaval. 



Veins from the large and small intestines unite to form the mesen- 

 teric vein which is joined as it progresses forward by the splenic vein 

 from the spleen, pancreatic veins from the pancreas, and gastric 

 veins from both sides of the stomach. The vessel resulting from 

 these unions is the hepatic portal vein. It passes through the anterior 

 portion of the pancreas and sends a large branch into the lower left 

 lobe of the liver. At about this point it often receives a final gastric 

 branch which has passed on top of the pancreas to join it. It then 

 continues a short distance to join the abdominal vein just below the 

 heart. 



The abdominal vein arises as follows: Two large veins, the sciatic 

 and femoral, bring blood from the hindlimbs. The femoral, as it 

 enters the body cavity, gives off the pelvic vein. The pelvic veins from 

 each side of the body join in the middle to form the large ventral 

 abdominal vein. As the abdominal vein runs toward the heart along 

 the median portion of the ventral body wall, it receives vesicular veins 

 from the bladder, parietal veins from the body wall and, at its ante- 

 rior end, a cardiac vein from the heart. In the region of the liver 

 it leaves the body wall, is joined by the hepatic portal vein, and enters 

 the right and upper left lobes of the liver by short branches, dis- 

 charging its blood into sinusoids. 



The Renal Portal System. — This system, like the hepatic portal 

 system, diverts blood to a purifying organ instead of carrying it 

 directly to the heart. In this ease, the blood is taken to the kidneys. 



The outer femoral vein and the medial sciatic vein collect blood 

 from the hindlegs. The femoral vein, after giving off the pelvic vein, 

 runs anteriorly and joins the sciatic, to make the renal portal vein. 

 Near the kidney this vein receives the dorsolumbar vein from the body 



