AMPHIBIA 213 



the liver, where it obtains the hepatic veins, and runs forwards 

 to enter the sinus venosus. 



There are, in addition, two important portal systems. 

 The blood coming from each of the hinder limbs by the femoral 

 and sciatic veins is poured by these into a single vessel at the 

 posterior end of the body cavity. This is the renal portal vein, 

 and it is directed forwards on the outer margin of the kidney. 

 In the kidney the blood from the renal portal is passed into 

 superficial venous spaces, which are supplied also by the blood 

 derived from the renal arteries, and the mixed blood leaves the 

 kidney by the renal veins. 



The femoral vein, before fusing with the sciatic to form the 

 renal portal, gives off a pelvic vein. The two pelvic veins unite 

 to form the abdominal vein which runs along the body wall. 

 The abdominal vein receives blood from the bladder by the 

 vesical vein and from the body wall throughout its length. 

 The abdominal vein quits the body wall opposite the liver, and 

 after receiving the cardiac vein from the conus arteriosus 

 it splits into two vessels which enter the two lobes of the 

 liver. 



At the point of bifurcation the abdominal vein receives 

 the hepatic portal vein, a vessel which brings blood from the 

 stomach, intestine, and spleen, and which before joining the 

 abdominal vein sends a branch to the left lobe of the liver. 



The liver thus obtains blood from the legs, the bladder, the 

 body wall, and the alimentary canal, and this blood, together 

 with that derived from the hepatic artery, is mixed in the 

 capillaries of the liver and reaches the hepatic veins, and so 

 the posterior vena cava. 



In addition to the blood system the frog possesses a lymph 

 system which reaches a high degree of development. It is 

 later in appearance than the blood-vessels, and originates in 

 spaces in the mesenchyme from the exudation of the plasma 

 and leucocytes from the vessels, an exudation which brings 

 oxygen and food into immediate relationship with the cells. 

 Between the skin and body wall and the muscles of the limbs 

 wide spaces, known as subcutaneous lymph sacs, are formed, 

 and similar spaces occur between the peritoneum and the 

 body wall dorsally. These and smaller spaces elsewhere 



