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 opal- 

 escent, 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 dextrin 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 may be freed from adherent proteids by 

 being boiled with an alcoholic solution of potash in which it 

 is insoluble, or by other means, and if subsequently 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 



