DIGESTION OF FOOD: THE INTESTINE 101 



beef's liver as it hangs in the markets. This red color is partly 

 due to the fact that the organ is very full of blood; it has been 

 estimated that one-quarter of all the blood of the body may 

 be in the liver. Its surface shows 

 a mottled appearance, due to the 

 arrangement of tissues in the organ, 

 for it is really a large compound 

 gland; Fig. 54. 



Beneath the right lobe is the 

 gall bladder, a pear-shaped sac, 

 about four inches in length, and 

 at its widest place an inch in 

 diameter. Its function is that of FlG - 54. THE SURFACE OT 

 a storage reservoir for holding the THE LIVER 



, , , , r , ... Slightly magnified 



bile secreted by the liver when it is 



not needed in the intestine. From an examination of Figure 

 52, it will be seen that the bile does not run directly from the 

 liver into this sac, but that the only duct leading away from 

 the organ, the hepatic, goes in a fairly direct line to the first 

 loop of the intestine. A side branch from this, the cystic 

 duct, leads to the gall bladder; from their junction to the 

 intestine, is a tube called the common bile duct. 



The liver keeps steadily secreting but the demand for bile 

 is not constant, as food conditions in the intestine are not 

 always the same. When bile is not needed in the intestine 

 the common bile duct closes, and the bile, then coming from 

 the liver, goes back and is stored in the gall bladder (Fig. 48) ; 

 there it accumulates until the opening into the intestine 

 again allows a free flow. The presence of chyme coming from 

 the stomach causes such an opening. 



The large size of the liver and its abundant blood supply 

 suggest that the organ must have very important uses. The 

 amount of fluid which it secretes daily varies in different per- 

 sons from a pint to a pint and a half; it is a little thicker than 

 water, and of a golden brown color. Notwithstanding this 



