176 VERTEBRATE ZOOLOGY 



Exercise 12. Draw the dorsal aspect of the heart, together with the 

 precaval and pulmonary veins and their branches, so far as these 

 have been observed. 



Follow the postcaval vein backward through the right lobe of 

 the liver. Note the hepatic veins, which enter it in the liver. 

 Turn the right lobe over to the animal's left and note where the 

 postcaval vein enters it from behind. Posterior to this point and 

 near the anterior end of the kidneys, the postcaval is formed by 

 the union of the two iliac veins. 



Each iliac vein is formed in the mass of the anterior lobe of 

 the kidney by the union of three veins: the renal portal, the 

 anterior renal, and the femoral vein. The last of these veins 

 comes from the leg and will be seen approaching from the side 

 and lying between the first and second lobes of the kidney. The 

 renal portal has already been mentioned. It enters the hinder 

 lobe of the kidney, after first receiving the internal iliac vein from 

 behind, and passes forward, imbedded in the kidney, giving off 

 numerous small branches. It thus constitutes a portal vein, inas- 

 much as it distributes blood to the kidney instead of sending it 

 directly to the heart. Instead of entirely breaking up, however, 

 into small veins and capillaries, as does the renal portal of the 

 lower vertebrates, it soon begins to increase in size and joins 

 the iliac. Consequently only a portion of the blood brought to 

 the kidneys by the renal portal veins is distributed throughout 

 them; the greater part probably goes directly to the iliacs and 

 the heart. 



The anterior renal vein is a large longitudinal vein which ap- 

 pears on the ventral surface of the kidney near the median line, 

 imbedded in it. 



Carefully follow the renal portal forward by picking away the 

 substance of the kidney which surrounds it, until it joins the 

 iliac vein. Follow the anterior renal and the femoral vein to 

 the iliac. Follow the femoral vein into the leg and observe its 

 branching. 



Exercise 13. Draw a semidiagrammatic view of the postcaval vein 

 and its branches, together with an outline of the organs in which 

 the veins lie. 



