Till: IIKART 93 



subclavian, jugular, and other veins of each side unite, and the 

 two l.u-e veins so formed join to form the superior vena 

 .iv. i, whi'-h empties its blood into the right auricle. The large 

 veins from the legs unite to form the inferior vena cava, which 

 passes up the abdomen, receiving the veins from the kidneys, 

 and close below the diaphragm a large vein, the hepatic 

 vein, from the liver ; it then pierces the diaphragm and 

 reaches the right auricle. The veins from all the other 

 abdominal organs, namely, the stomach, the small intestine, the 

 large intestine, the spleen, and the pancreas, unite to form a 

 large vein called the portal vein. The portal vein runs to 

 the liver. In the liver the portal vein breaks up into capillaries, 

 and its blood mingles with the blood brought to the liver 

 direct from the aorta. The blood flows from the liver by the 

 hepatic vein to the inferior vena cava. So that the blood 

 from these abdominal organs only reaches the inferior vena 

 cava to return to the heart, after it has passed through a 

 second set of capillaries in the liver. 



Observation of the Beat of the Heart of the Prog. 

 Kill a frog by cutting off its head. With a pair of scissors 

 cut through the skin and the sternum exactly in the middle 

 line in front. The heart will then be seen. The heart, like 

 the other tissues of the frog, remains living for some time after 

 the death of the animal, and will continue to live when even 

 cut out of the body. Observe the beating of the heart. The 

 two auricles contract and then immediately the ventricle (there 

 is only one ventricle in the frog). The auricles, which are 

 red in colour, the right one being dark, become suddenly paler 

 when they contract, as the blood in consequence is driven out 

 of them into the ventricle. Similarly when the ventricle 

 contracts it becomes smaller and paler as the blood is driven 

 out of it into the arteries. In the frog there are two other 

 contractile parts, viz. (i) the ends of the great veins, which are 

 dilated, forming a venous chamber called the sinus venosus just 

 before they open into the auricles, and (2) the root of the 

 X real arteries, or bulbus arteriosus. The sinus venosus contracts 

 first, then the two auricles together, then the ventricle, and 

 then the bulbus arteriosus. 



