86 HUMAN PHYSIOLOGY. 



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

 by the inspiratory movements of the diaphragm, the contraction of the mus- 

 cular fibres 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 leads to an accu- 

 mulation within the bile ducts. The pressure within the ducts increasing 

 beyond that of the blood within the capillaries, a re absorption 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 constitu- 

 ents 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 chemical composition 

 to starch, which he terms glycogen ; also that when the liver is removed 

 from the body, and its blood vessels 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 Trommer's or Fehling's 

 tests, 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 cent, is 

 formed when the animal is fed on starchy and saccharine, than when fed on 

 animal food. The glucose, 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 cir- 

 culation, it is probable that it is detained in the liver, dehydrated and stored 

 up as glycogen. The change is shown by the following formula : 



Glucose. Water. Glycogen. 



C 2 H 12 6 -H 2 = 



The glycogen thus formed is stored up in the hepatic cells for the future 

 requirements of the system. When it is carried from the liver it is again 

 transformed into glucose by the agency of a ferment. Glycogen does not 

 undergo oxidation in the blood ; this takes place in the tissues, particularly 



