SEC. 2. THE HISTORY OF GLYCOGEN. 



453. If the liver of a well-fed animal be removed immedi- 

 ately after death, rapidly divided into small pieces, thrown into 

 boiling water, rubbed up and boiled, a decoction may be obtained 

 which after careful neutralisation and filtration will be tolerably 

 free from proteid matter. Such a decoction is remarkably opa- 

 lescent, milky in fact in appearance, much more so than a 

 similar decoction from muscle or other tissue, and remains 

 opalescent even after repeated filtration. Treated with iodine, the 

 solution turns a brownish red, port-wine red colour, not unlike 

 that given by dextrine when iodine is added ; the colour disap- 

 pears on warming, but reappears on cooling provided that not too 

 much proteid matter has been left in the solution. Treated with 

 Fehling's fluid or other tests for sugar, the solution is found to 

 contain a small and variable, but only a small, quantity of sugar. 



If the solution be exposed, preferably in the warm, to the 

 action of saliva or of some other amylolytic ferment, or be boiled 

 with dilute acid, the opalescence disappears ; and the now clear 

 transparent solution gives no longer the port-wine reaction with 

 iodine. Tested moreover with Fehling's fluid or by other means 

 it is now found to contain a considerable quantity of sugar. 



If alcohol be added to the opalescent solution until the mixture 

 contains 60 p.c. of the alcohol (previous concentration by evapora- 

 tion being desirable) a white amorphous precipitate is thrown 

 down. This precipitate, removed by filtration, boiled with an 

 alcoholic solution of potash in which it is insoluble, but which 

 dissolves and destroys any proteids which may be present, treated 

 with ether to remove fatty impurities, and washed with alcohol 

 may be obtained in a pure condition. It then appears as a white 

 amorphous powder, fairly soluble in water, but always giving rise 

 to a milky opalescent solution unless an excess of alkali be present, 

 in which case the opalescence may be slight or absent. 



The opalescent solution of this purified material gives a port- 

 wine reaction with iodine, but no reaction whatever with Fehling's 

 fluid or the other sugar tests. Treated with an amylolytic ferment 



