BULLFROG AS TYPICAL VERTEBRATE ANIMAL 73 



liver; and continues to the ventral side of the stomach, where it is 

 distributed. The anterior mesenteric artery gives off the splenic 

 (lienal) artery to the spleen and then divides into two parallel 

 vessels which send numerous smaller arteries to the small and large 

 intestines. 



The urinogenital arteries consist of about four to six small mucli- 

 divided arteries which are given off from the ventral side of the dorsal 

 aorta to right and left, supplying the kidneys, reproductive organs, 

 and fat bodies, A few small lumbar arteries arise either as branches 

 of these or directly from the aorta and go to the body wall on each 

 side. The small posterior mesenteric artery is given off near the 

 posterior end of the aorta, passing to a portion of the rectum and, 

 in the female, to the ovisac. 



Near the posterior end of the body cavity the dorsal aorta divides 

 into two iliac arteries going to the hind legs. Each of these gives 

 off (1) an epigastric artery supplying the bladder and dorsal and 

 ventral body walls of the region, and (2) just below it, a femoral, 

 artery passing to the body wall, skin, and proximal muscles of the 

 thigh. As the iliac artery enters the leg, a rectovesical artery is sent 

 off to the rectum, bladder, and skin on the dorsal surface of the 

 thigh. In the upper leg the continuation of the iliac, now called the 

 sciatic, gives off a branch to the right and to the left, supplying the 

 muscles, and then continues down the leg, sending off several branches 

 at the knee. 



The pulmocutaneous arch takes blood to the respiratory organs: 

 the lungs, skin, and buccopharyngeal cavity. The pulmocutaneous 

 arch on each side divides into a pulmonary artery to the lungs and 

 a large cutaneous artery, which passes outward to the skin. 



The Veins 



The veins usually parallel the arteries that brought blood to the 

 tissues from which the veins are returning it. The walls of the 

 veins are thinner and not as elastic as those of the arteries." Many 

 veins, particularly those of the limbs, have semilunar valves on the 

 internal surface of the wall which open in the direction of flow and 

 prevent the backflow of blood. 



In returning blood to the heart, the venous system carries some of 

 the blood through the kidneys or through the liver, providing renal 



