400 DISSECTION OF THE PIGEON 



a. The posterior mesenteric vein is a median vein, 



running backwards in the mesentery supporting 

 the rectum : it collects the blood from the hinder 

 part of the small intestine, and from the rectum 

 and cloaca. It receives a very small median 

 caudal vein from the tail ; and divides, opposite 

 the posterior end of the kidneys, into right and 

 left hypogastric veins. 



b. The hypogastric vein, on each side, receives the 



internal iliac vein from the inner surface of the 

 pelvic cavity, and enters the kidney at its pos- 

 terior end : it then runs forwards through the 

 posterior and middle lobes of the kidney, to open 

 into the femoral vein, in the groove between the 

 middle and anterior lobes. 



c. The femoral vein, on each side, returns the blood 



from the leg. Entering the kidney at its outer 

 side, between the middle and anterior lobes, it 

 receives, as just noticed, the hypogastric vein : 

 a little further on, the renal vein, returning blood 

 from the two hinder lobes of the kidney, joins it 

 to form the iliac vein. 



d. The iliac vein, formed in this way by the junction 



of the femoral, hypogastric, and renal veins, 

 leaves the kidney at its inner border, between its 

 anterior and middle lobes ; and then runs forwards, 

 uniting opposite the anterior 'end of the kidney 

 with the iliac vein of the other side, to form the 

 posterior vena cava, 



3. The hepatic portal system. 



The portal vein lies in the omentum, between the 

 two bile-ducts, and on reaching the liver divides into 

 two branches, one supplying each lobe. It conveys 

 to the liver the blood from the greater part of the 

 length of the alimentary canal, and is formed by the 

 union of three chief veins. 



