THE RABBIT 2O3 



systems, showing their relation. Tie the bladder at its 

 base and remove it, cutting behind the place tied. 



(9) Circulation and Circulatory System. — (a) Cut 

 the diaphragm away and study the heart. Where is it ? Is 

 it an advantage to have it on the side rather than in the 

 middle part of the body? Note its shape and relative po- 

 sition with reference to lungs and esophagus. 



(b) Note the large dark blood vessel, the vena cava, 

 extending from the liver across to the heart. Where does 

 it enter the heart? Lift up the lobes of the liver and trace 

 the vena cava back and find the hepatic vein running from 

 the liver into the vena cava. Look in the mesenteries which 

 have been cut from the stomach and intestines for a large 

 dark blood vessel which seems to be formed from the veins 

 returning from the alimentary canal. Trace it to the liver. 

 It is the portal vein. What does it contain besides impure 

 blood? Trace the large vein backward and note the veins 

 coming from the kidneys, the renal veins, to the place where 

 the veins from the legs unite to form it. Do you notice any 

 sudden change of size? Where? 



Trace the veins on the right side of the heart forward 

 toward the head. Do you find a union of two veins just 

 anterior to the heart? The vein from the head, the right 

 jugular, unites with the vein from the shoulder, the right 

 subclavian. The union of these forms the right anterior 

 vena cava. Trace it to the right auricle. On the left side 

 find a similar vessel, the left anterior vena cava, formed by 

 the union of the left jugular and the left subclavian veins, 

 and crosses at top of left lung, emptying into the right 

 auricle. On the left side find a similar vessel, the left an- 

 terior vena cava, formed by the union of the left jugular 



