DIGESTIVE SYSTEM. 327 
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 opimion. 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 te 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 imto 
a particular receptacle, termed the gallbladder. 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- 
dochus. . 
Let us now attend to the nature of the bile itself; a 
fluid which has long occupied the attention of the physio- 
