CHAPTEE XI. 



PRODUCTION OF GLYCOGEN AND GLUCOSE IN THE 



LIVER. 



IP the liver of a carnivorous or herbivorous animal, after twenty-four 

 hours' fasting, be taken from the body immediately after death, finely 

 divided, and boiled for a few moments in water with animal charcoal or 

 an excess of sodium sulphate, to eliminate the albuminous and coloring 

 matters, the filtered fluid will be nearly clear, or show only a moder- 

 ately opaline tinge. But if the same thing be done within a few hours 

 after the ingestion of animal or vegetable food, the watery decoction of 

 the liver tissue will be strongly opalescent, being rendered turbid by 

 the presence in considerable quantity of a matter which communicates 

 to the solution a partial turbidity. This matter is glycogen, which is 

 contained, in greater or smaller quantity, in the liver extract under these 

 two conditions. 



This substance, first discovered by Bernard, has so strong an analogy, 

 in its composition and properties, with the ordinary amylaceous matter 

 of vegetable tissues, that it is often spoken of as "animal starch." It 

 is, when purified, a non-nitrogenous body, having the formula C 6 H 10 5 . 

 It is accordingly a carbohydrate, and indentical with starch in its ulti- 

 mate chemical composition. 



It is obtained from the liver by first cutting the organ into small 

 pieces and immediately coagulating them by a short immersion in boil- 

 ing water. This is for the purpose of prevening the partial transforma- 

 tion of the glycogen which would otherwise take place, under the influ- 

 ence of a moderate temperature, by contact with the albuminous matters 

 present in the liver. These albuminous matters having been once 

 coagulated by the preliminary boiling, the glycogen can afterward be 

 extracted at leisure. The liver tissue is then ground to pulp in a 

 mortar and boiled continuously for half an hour with a small quantity 

 of water, just sufficient to keep the mixture fluid, in order to obtain a 

 decoction as concentrated as possible. The decoction is then treated 

 with animal charcoal, to remove the coloring matters, and filtered. The 

 solution is distinctly opaline, and if allowed to fall into a vessel of strong 

 alcohol, the glycogen, which is insoluble in this fluid, is precipitated in the 

 form of a white deposit. This deposit is still contaminated by a little 

 glucose, and by a certain quantity of biliary salts and other nitrogenous 

 matters. The glucose and biliary salts are removed by repeatedly 

 washing the precipitate with alcohol. The deposit is then boiled for 

 a quarter of an hour with a concentrated solution of potassium hydrate, 

 ( 228 ) 



