i8o ELEMENTARY BIOLOGY. [CHAP. 



d. The dorso4umbar vein, which lies along the 

 transverse processes of the vertebrae and receives 

 blood from the walls of the abdomen and from 

 the interior of the spinal canal, opens into the 

 common iliac. 



3. The system of the anterior abdominal vein, formed 

 by the union of the ventral ends of the pelvic veins 

 (2. b.). It receives blood from the urinary bladder 

 and the walls of the abdominal cavity, and at its 

 anterior end divides into two branches a right and 

 a left. These branches go to the corresponding 

 lobes of the liver, the left receiving a large commu- 

 nicating branch from the gastric division of the vena 

 portce. 



4. The system of the vena portce formed by the union 

 of two veins; one, gastric, which brings back the 

 blood from the stomach, the other, lieno-intestinal, 

 which returns that from the spleen and intestines. 



[Hence the right lobe of the liver and part of the left 

 lobe are supplied with systemic venous blood, more 

 or less mixed with gastric venous blood, while only part 

 of the left lobe is supplied with intestinal venous blood. 

 Besides this venous blood, it must be recollected that 

 the liver receives arterial blood by the hepatic artery.] 



5. The system of the pulmonary vein, formed by the 

 union of the veins of the right and left lungs. 



In addition to the apparatus of the circulation of the 

 blood, the Frog possesses two pairs of lymph-hearts. These 

 are contractile muscular sacs, which are connected on the 

 one hand with the lymphatic vessels and on the other with 

 large veins in their neighbourhood; and which pump the 



