76 VERTEBRATE ZOOLOGY 



from the digestive tract and the spleen, and the latter from the 

 hinder part of the body. These two veins meet near the posterior 

 end of the duodenum, close to the dorsal surface of the liver ; they 

 are here entirely embedded in the pancreas. The single vessel thus 

 formed passes at once to the liver, where it breaks up into branches 

 which distribute blood to all parts of that organ. 



Follow the abdominal vein forward to the hepatic portal. 

 Scrape away the pancreas, and note that the hepatic portal is 

 formed by the meeting of three large veins,— the mesenteric, gas- 

 tric, and splenic. 



The mesenteric vein is the large longitudinal vein which lies in 

 the intestinal mesentery; it extends the entire length of the in- 

 testine and receives numerous intestinal veins, which bring blood 

 from its walls. The splenic vein comes from the spleen. The gas- 

 tric vein lies along the stomach and the dorsal surface of the liver. 



The renal portal system is formed on each side of the body by 

 the union of the pelvic, femoral, and caudal veins, which meet and 

 form the renal portal vein ; the system is joined with the hepatic 

 portal system by the abdominal vein. 



Trace this last-named vein back to the hinder part of the 

 abdominal cavity; it will be seen to be formed by the union 

 of two prominent veins, the right and left pelvic veins, one of 

 which will have been cut by the first incision. Trace the pelvic 

 vein backward; it is formed by the union of the femoral vein, 

 which comes from the hind leg, and the renal portal vein, which 

 goes to the side of the kidney. This latter vein enters the kidney 

 and distributes blood throughout that organ. 



Blood from the tail is brought forward by the caudal vein. This 

 vein runs just beneath the spinal column of the tail to the hinder 

 end of the abdominal cavity ; here it divides into two veins, each of 

 which goes to the lateral side of the kidney and joins the renal 

 portal vein. 



Exercise 14. Draw a diagram of the two portal systems. 



The remaining systemic veins may be divided into two groups, 

 those coming to the heart from the forward part of the body and 

 those coming from the hinder part. 



