ANATOMY OF THE FROG 55 



sciatic vein to form the renal-portal. The femoral and sciatic 

 veins are further connected by a small vessel, the ramus com- 

 municans iliacus, which runs transversely from one to the 

 other at the base of the thigh. The second or ventral branch 

 of the femoral vein is known as the pelvic vein ; it passes 

 inward towards the mid-ventral line of the abdominal wall, 

 and unites, just in front of the pubic cartilages, with its fellow 

 of the opposite side to form the anterior abdominal vein. 

 This is a large, median, unpaired vessel, which receives at its 

 point of origin the vesical vein from the bladder, and then 

 courses forward in the middle line of the ventral wall of the 

 abdomen till it reaches the xiphoid cartilage of the sternum. 

 It then turns inward and divides into three branches, two 

 lateral and one median. The two lateral branches pass to the 

 right and left lobes of the liver respectively, and break up in 

 its substance into capillaries ; the median branch unites with 

 the hepatic portal vein. 



The last-named vessel brings blood from the stomach and 

 intestines. It is formed by the union of the intestinal, gastric 

 and splenic veins, runs forward in the mesentery, and passes 

 into the left lobe of the liver, where it breaks up into 

 capillaries. Just before it enters the liver the hepatic portal 

 vein is joined by the descending branch of the anterior 

 abdominal. The blood from the liver is collected by the right 

 and left hepatic veins, which open into the inferior vena cava 

 just before it passes into the sinus venosus. We have seen 

 that the lungs are supplied with blood by the two pulmonary 

 arteries, each of which courses down to the outer surface of 

 the lung sac to which it belongs from base to apex, giving off 

 a number of branches as it goes. The blood, after passing 

 through the lung capillaries, is gathered by venules, which unite 

 to form the venous vessel lying along the inner side of the 

 base of each lung. These right and left pulmonary veins run 

 above the corresponding venae cavae, and unite to form a 

 single trunk, the common pulmonary vein, which opens into 

 the left auricle. We are now in a position to review the 

 course of the circulation of the blood in the frog. The blood 

 from the head and fore limbs, as well as that brought back by 

 the musculo-cutaneous veins, passes straight into the sinus 

 venosus by way of the superior venae cavae. But the blood 

 coming from the hind limbs and from the posterior part of 



