THE FROG AND VERTEBRATES IN GENERAL 195 



wall, hind limbs, etc., as follows : The liver receives venous blood 

 from (a) the single, median abdominal vein, which in turn arises 

 from a pair of pelvic veins ; and from (6) the intestinal tract 

 through the hepatic portal vein. The kidney receives venous 

 blood from a pair of renal portal veins which arise from the 

 femoral and sciatic veins of the hind limbs. (W. f. 121.) 



Arteries. The conus arteriosus, which as previously noted 

 leads from the ventricle, supplies all the arteries in the body. It 

 passes anteriorly from the ventricle and, just beyond the anterior 

 edge of the auricles, divides to form a right and left branch, from 

 each of which arises three arteries ; thus forming a total of six main 

 arteries, or three pairs, from the heart. These are designated as a 

 pair of common carotids, a pair of pulmocutaneous, and a pair 

 of systemic arches. 



Each of the common carotid arteries divides into an external 

 and an internal carotid, and these run anteriorly and supply 

 the entire head region. They each give off a number of branches 

 as they proceed. The pulmocutaneous arteries carry blood to 

 the respiratory organs. Each divides into two main branches, one 

 of which runs to the lungs (pulmonary artery) and the other 

 (cutaneous artery) to the skin and body wall. Each of the 

 systemic arteries curves dorsally and posteriorly. Posterior to 

 the heart, and close to the dorsal body wall, the two arches unite to 

 form a single large vessel, the dorsal aorta, from which branches 

 arise that supply the important abdominal organs, the muscles 

 of the abdominal body wall, and the hind legs. Before uniting to 

 form the dorsal aorta, the right and left systemic arches on each 

 side give off two branches : (a) the occipito-vertebral, from 

 which arise the occipital artery supplying the jaws and nose, 

 and the vertebral artery which runs to the vertebral column ; 

 and (6) the brachial artery which is distributed to the fore limb 

 of that side and to the body wall near by. (W. f. 121.) 



Portal Systems. Attention should be called to the renal 

 portal system and the hepatic portal system. The renal portal 

 system consists of a pair of veins which carry blood from the hind 

 limbs to the kidneys. Into each of these renal portal veins three 

 vessels empty : a femoral and a sciatic vein from the hind leg, 

 and a small dorsolumbar vein from the body wall. Thus, in the 

 Frog the venous blood from the hind limbs and from a portion of 

 the body wall, instead of emptying directly into the vena cava, 



