SEC. 1. THE HISTORY OF GLYCOGEN. 



357. 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 neutralization and filtration will be toler- 

 ably free from proteid matter. Such a decoction is remarkably 

 opalescent, milky in fact hi 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 

 disappears on warming, but reappears on cooling provided that 

 not too much proteia matter has been left in the solution. 

 Treated with Fehling's fluid or other tests for sugar, the solu- 

 tion 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 boil-d 

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

 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 romvntration 

 by evaporation being desirable) a white amorphous pivripitate 

 is thrown down. This precipitate, removed by filtration, boiled 

 with an alcoholic solution of potash in whu-h it is insoluble, but 

 which dissolves and destroys any proteids which may be pres- 

 ent, treated with ether to remove fatty impurities, and washed 

 with alcohol may be obtained in a pure condition. It tlu-n 

 appears as a white amorphous powder, fairly soluble in \\ 

 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 

 36 501 



