2*20 CIRCULATORY SYSTEM. 



course; but these are too variable in their number and distribu- 

 tion to come very usefully into any general description. 



The vena saphena minor springs from the small metatar- 

 sal vein. It runs directly up the back of the hock, over the root 

 of the OS calcis, and pursues its course upward along the front of 

 the gastrocnemii, and ultimately joins the femoral vein. It anas- 

 tomoses with the greater saphena, and receives in its course both 

 cutaneous and muscular branches. 



The Vena Porta. 



The veins of the chylopoietic organs have a peculiar and dis- 

 tinct arrangement from those of the body in general, and on this 

 account a separate description is commonly given of them. They 

 receive blood, as has been already seen, in a similar manner to 

 other parts ; but they return their blood into a channel which con- 

 veys it all through tlie liver, instead of conducting it immediately 

 into the vena cava posterior: this channel is the vena portse, a 

 vessel principally formed by the union of the splenic and mesen- 

 teric veins, though it is likewise contributed to by veins coming 

 both from the stomach and pancreas. 



The splenic vein, in company with its artery, occupies the 

 fissure of the spleen, makes a circuit in a flexuous manner towards 

 the right side, receiving in its way branches from the stomach, 

 omentum, and pancreas, besides all the veins of the spleen, and 

 at length ends in the vena porta. 



The mesenteric veins, anterior and posterior, bear much 

 correspondence to their arteries. T/ie anterior one is of large 

 size, being constituted of those numerous ramifications which 

 diverge over the small intestines, together with the arteries : it 

 also receives branches from the coecum and ccecum caput coli, 

 some few from the stomach, and some from the pancreas. The 

 posterior mesenteric runs obliquely forward, after having received 

 branches correspondent to those of its fellow artery. 



The vena portce is concealed at its origin by the pancreas ; im- 

 mediately above which its formation takes place. From this it 

 runs under the beginning of the duodenum, on the right of the 

 hepatic duct and artery, and makes its way to the concave part 

 of the liver. About opposite to the centre of the right lobe, the 

 vein splits into two divisions: the right immediately enters the 

 substance of that lobe; the left is continued forward along with 

 the hepatic artery, and, the same as that vessel does, bifurcates 

 to supply the left and middle lobes. 



