3 i2 SCIENCE PROGRESS. 



of glycogen. The glycogen is most abundant after carbo- 

 hydrate food ; but it also occurs in animals kept on a pro- 

 teid diet. In the latter case it must originate by complex 

 intra-protoplasmic or metabolic changes. In the former 

 case it is probably a storage of reserve carbohydrate, and 

 the chemical processes involved are simpler. C. Voit and 

 his pupils (i) have taken up this subject and by experi- 

 ments on rabbits and hens investigated what forms of car- 

 bohydrate may be stored up in the liver as glycogen. The 

 hepatic glycogen was first reduced to a minimum by a few 

 days' inanition. Large doses of different sugars were then 

 given, the animal killed and the estimation of the glycogen 

 performed either by Briicke's or Kulz's method. 



Dextrose, levulose, cane sugar and maltose increased 

 the glycogen ; lactose and galactose did not, or only very 

 slightly. In the alimentary canal cane sugar is inverted, 

 equal parts of dextrose and levulose being formed from it. 

 Maltose undergoes a corresponding hydrolytic change, two 

 molecules of dextrose beino- formed from it. The liver, in 

 other words, forms glycogen from those sugars which are 

 converted into dextrose and levulose before they reach it. 

 In fact, these appear to be the only forms of sugar which 

 when present in the blood lead to a storage of glycogen in 

 the liver ; when subcutaneously injected the hepatic glyco- 

 gen rises in amount. No other form of sugar behaves in 

 this way. In regard to levulose (a ketone) a point still 

 unsettled is whether the liver cells form glycogen from it 

 direct, or after previously changing it into the corresponding- 

 aldehyde, dextrose. E. Fischer's researches would indicate 

 that the latter possibility is not improbable ; moreover the 

 action of the cells of the mammary gland in converting 

 dextrose into lactose is somewhat analogous. 



Questions of this kind derive practical importance be- 

 cause the subject of glycogen forms the starting-point for 

 the consideration of the pathological condition called dia- 

 betes, and F. Voit (2) carried on the research on a diabetic 

 patient, who was taking restricted diet, and the amount of 

 suo-ar in whose urine was thus reduced to a low ebb. On 



O 



one occasion 100 grammes, on another 150 grammes ol 



