328 DISSECTION OF THE RABBIT 



the pubic symphysis. They receive small veins 

 from the bladder [and in the female from the 

 uterus]. 



They are direct continuations of the 

 femoral veins, which lie along the inner or 

 preaxial borders of the thighs. 



vii. The internal iliac veins return blood from the 

 backs of the thighs, and, running forwards 

 through the pelvic cavity, unite about half an 

 inch behind the external iliacs to form the 

 commencement of the posterior vena cava. 



2. The portal system consists of the veins returning blood 

 from the whole length of the alimentary canal from 

 the stomach backwards, and also from the pancreas 

 and spleen. These veins lie in the mesentery, and 

 converge to form the main trunk, or portal vein, 

 which lies close alongside the posterior vena cava 

 and, entering the liver, divides into branches supply- 

 ing its several lobes. 



The portal system can readily he seen in a freshly killed 

 animal on opening the abdomen and turning the viscera aside. 

 The veins are of large size and usually gorged with blood, 

 and care must be taken not to injure them, as they bleed very 

 freely. 



The following are the main trunks which unite to 

 form the portal vein. 



i. The lieno-gastrie vein returns blood from the 

 walls of the stomach and from the spleen. 



ii. The duodenal vein returns blood from the 

 duodenum and pancreas. 



iii. The anterior mesenteric vein is formed by the 

 union of veins from the whole length of 

 the small intestine, and from the caecum, the 

 colon, and the greater part of the length of 

 the rectum. 



