DIGESTIVE SYSTEM. 37 



This vein is termed the vena portarum. It is formed from 

 the union of the branches of nearly all the veins which 

 arise from the abdominal viscera. Both these vessels spread 

 their minute ramifications throughout the liver, and both 

 their extreme divisions terminate in true veins. Whether, 

 then, is the bile prepared from venous or arterial blood ? 

 In the mammalia, it is probable that while the latter serves 

 for the nourishment of the liver, the former furnishes the 

 materials for the formation of the bile. The peculiar ter- 

 mination of the vein, its superior size, when compared with 

 the artery, appear to countenance such an opinion. On the 

 other hand, instances have occurred, in which this vein did 

 not terminate in the liver ; consequently, the bile must have 

 been derived solely from the hepatic artery. But these ex- 

 treme cases do not enable us to determine the nature of the 

 different parts of the organ in a sound state ; although they 

 furnish us with interesting displays of the compensating 

 power of nature. 



The bile is collected in the liver by very minute delicate 

 vessels, which, by their union, form the hepatic duct. 

 Sometimes, instead of forming a single duct, the bile is 

 conveyed by several canals to the stomach or intestine. In 

 some cases, the hepatic duct conveys the bile directly to its 

 destination ; in other cases, a portion of it is diverted into 

 a particular receptacle, termed the gall-bladder. The 

 structure of the coats of this reservoir is similar to that 

 of the stomach. In shape and size this bladder varies ac- 

 cording to the species. The canal by which it is filled, and 

 by which it is likewise emptied, is termed the cystic duct. 

 The canal which is formed by the union of the hepatic and 

 cystic ducts, has been denominated ductus communis chole- 

 dockus. 



Let us now attend to the nature of the bile itself; a 

 fluid which has long occupied the attention of the physio- 



