In order to determine, whether glycogen formation from glucose or fructose takes place by the macerated liver- or muscule-substance with the sugar saline solution or in the liver, which was isolated from the blood circulation and perfused with the sugar saline solution, and furthermore the influence of insulin on this process I chose for this investigation the organs of Bufo japonicus which are most suited to such purpose: 1. Macerated liver substance has no ability to form glycogen neither from glucose nor fructose. 2. Excised muscle is able to form glycogen from glucose but not from fructose. 3. Addition of insulin into the macerated organmass reduces the glycogen contents both in liver and muscle. 4. The reduction of glycogen contents in the excised liver or muscle is accerelated by the addition of insulin. Even in excised liver, which has no ability to form glycogen from glucose or fructose, the presence either of these sugars retards the reduction of glycogen content. In muscle glucose has such effect but not fructose. 5. In the liver perfused with sugar saline solution occurs the glycogen formation from glucose or fructose. 6. Insulin accerelates the glycogen formation from fructose in the perfused liver but retards the same process from glucose.