GLYCOGBN AND ITS FORMATION. 353 



with those of the other leg, that have been contracting mean- 

 time and using up their glycogen." 



These facts clearly indicate that oxidation processes are 

 not in order here, since glycogen is a source of energy, intended, 

 therefore, for subsequent oxidation wherever it is distributed. 

 Indeed, Professor Foster remarks, in this connection: "It was 

 formerly believed that this sugar underwent an immediate and 

 direct oxidation as it was circulating in the blood. ... It 

 is sufficient for us at the present to admit that the sugar is 

 made use of in some way or other." Referring to the physio- 

 logical uses of glycogen, he also says: "The main purpose of 

 the deposition of glycogen is to afford a store, either general 

 or local, of carbohydrate material, which can be packed away 

 without much trouble so long as it remains glycogen, but which 

 can be drawn upon as a source of soluble circulating sugar 

 whenever the needs of this or that tissue demand it." That 

 the oxidizing substance has nothing to do with the process is 

 clear. 



The conversion of glycogen into sugar in the liver appears 

 as a wasted function, the carbohydrates having been already 

 split into dextrose or dextrose and levulose in the portal sys- 

 tem. Why they do not merely pass on to the several tissues 

 seems strange. But it soon becomes evident that, were it 

 otherwise, sugar would accumulate, then be excreted by the 

 kidneys, and lost, since there can only be a fixed and limited 

 (0.1 or 0.2 per cent.) amount of sugar in the circulation at a 

 given time. So useful a substance is, therefore, stored, after 

 dehydration, in the hepatic cell as glycogen, and converted into 

 sugar according to the needs of the organism. 



Conversion of the liver glycogen into dextrose is generally 

 ascribed to a special ferment, thought to originate in the liver, 

 but the nature of which has remained undetermined. The 

 experiment of Claude Bernard, upon which this view is mainly 

 based, is the following, as related by Stewart: "A rabbit, after 

 a large carbohydrate meal of carrots, for instance is killed 

 and its liver rapidly excised, cut into small pieces, and thrown 

 into acidulated boiling water. After being boiled for a few 

 minutes the pieces of liver are rubbed up in a mortar and again 

 boiled in the same water. The opalescent aqueous extract is 



