LIVER. 175 



then that the walls of the gall-bladder contract and discharge it 

 into the intestine. 



The flow of bile from the liver cells into the gall-bladder is 

 accomplished by the inspiratory movements of the diaphragm, and 

 by the contraction of the muscle-fibers of the biliary ducts, as well 

 as the vis a tergo of new-formed bile. Any obstacle to the outflow 

 of bile into the intestine leaps to an accumulation within the bile- 

 ducts. The pressure within the ducts increasing beyond that of the 

 blood within the capillaries, a reabsorption of biliary matters by 

 the lymphatics takes place, giving rise to the phenomena of jaundice. 



The bile is both a secretion and an excretion; it contains new con- 

 stituents, which are formed only in the substance of the liver, and 

 are destined to play an important part ultimately in nutrition ; it 

 contains also waste ingredients, which are discharged into the 

 intestinal canal and eliminated from the body. 



Glycogenic Function. In addition to the preceding function, Ber- 

 nard, in 1848, demonstrated the fact that the liver, during life, 

 normally produces a sugar-forming substance, analogous in its chemic 

 composition to starch, which he terms glycogen ; also that, when the 

 liver is removed from the body, and its blood-vessels are thoroughly 

 washed out, after a few hours sugar again makes its appearance in 

 abundance. 



It can be shown to exist in the blood of the hepatic vein as well 

 as in a decoction of the liver substance by means of either Trom- 

 mer's or Fehling's test, even when the blood of the portal vein does 

 not contain a trace of sugar. 



Origin and Destination of Glycogen. Glycogen appears to be 

 formed de novo in the liver cells, from materials derived from the 

 food, whether the diet be animal or vegetable, though a larger per- 

 centage is formed when the animal is fed on starchy and saccharin 

 than when fed on animal food. The dextrose, which is one of the 

 products of digestion, is absorbed by the blood-vessels and carried 

 directly into the liver; as it does not appear in the urine, as it 

 would if injected at once into the general circulation, it is probable 

 that it is detained in the liver, dehydrated, and stored up as glycogen. 

 The change is shown by the following formula : 



C 6 H 12 6 - H 2 = C 6 H 10 5 . 

 Dextrose. Water. Glycogen. 



