BULLFROG AS TYPICAL VERTEBRATE ANIMAL 75 



Each of the two anterior precavals receives blood from three 

 branches: (1) the external jugular bringing blood from the tongue, 

 hyoid, thyroid, pseudothyroid, and floor of the mouth; (2) the in- 

 nominate vein, made up of a fusion of the internal jugular returning 

 blood from the brain and other parts of the head, and the subscapular 

 vein bringing blood from the back of the arm and shoulder; and 

 (3) the subclavian vein, a fusion of the brachial vein, returning blood 

 from the forelimb, and the large musculocutaneous vein, which forms 

 an ellipse down the side of the body and extends up into the head 

 region, returning blood from the skin and outer muscles in these 

 regions. 



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 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 network 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 over the pancreas to join it. It then contin- 

 ues 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 

 aMominal vein. As the abdominal vein proceeds toward the heart 

 along the median portion of the ventral body wall, it receives vesical 

 veins from the bladder, parietal veins from the body Avail and, at its 

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



