BLOOD-VESSELS. 253 



join the subclavian. This, the lateral abdominal 

 vein, corresponds to the anterior abdominal 

 vein of the frog. The other paired vein is 

 the lateral cutaneous vein, which runs more 

 superficially from the tail right . up to the 

 Cuvierian sinus. 



2. The renal portal system. 



The blood from the muscles of the tail is returned 

 by the caudal vein, which lies below the caudal artery 

 in the haemal arches of the vertebrae. Opposite the 

 hinder ends of the kidneys the caudal vein divides into 

 the right and left renal portal veins, which run forwards 

 along the dorsal edges of the right and left kidneys 

 respectively, receiving branches from the body-wall, 

 and entering the kidneys along their whole length. 



Cut across the tail about two inches behind the cloaca. 

 Find the caudal vein lying in the hcemal arches of the vertebras, 

 ventral to the caudal artery ; trace the vein forwards with a 

 seeker, or inject it, and then dissect it out. 



3. The hepatic portal system. 



The hepatic portal vein is formed by the union 



of two veins, one from the main lobe of the spleen 



and the other from the intestine. It runs forwards 



in the mesentery along the dorsal border of the 



pancreas, and, receiving veins from the pancreas 



and from the stomach, enters the liver a little to 



the right of the median plane. 



Find the hepatic portal vein at the point where it enters 



the liver, a little to the right of the junction of the two lobes, 



and follow it backwards, turning aside the viscera as may be 



necessary, but not cutting anything. 



C. The Arterial System. 



The arterial system may conveniently be described under 

 three heads : (1) the afferent branchial vessels, which carry 

 the venous blood from the heart to the gills to be aerated ; 



T 



