752 



STORAGE OF GLYCOGEN. 



[BOOK ii. 



increase of glycogen, be supplied directly from the food. It seems 

 as if in the summer the frog lives up to its capital of hepatic 



B 



FIG. 92. THREE PHASES OF THE HEPATIC CELLS OF THE FROG. (Langley.) 



A. Cells rich in glycogen. Taken from a frog during winter. The cells are 

 large, and proteid granules are massed round the lumen, the homogeneous outer 

 zones of the cells being largely composed of glycogen which was -present in con- 

 siderable abundance. The outer zones contained numerous fat globules, shewn as 

 dark dots ; but as stated in the text these fat globules vary much. 



B. Cells poor in glycogen. Taken from a winter frog which had been kept at 

 22 C. for 10 days. The cells contain very little glycogen and the proteid granules 

 are dispersed throughout the cell. In a summer frog well fed on proteids the cells 

 would present a very similar appearance. 



C. Starved cells. Taken from a summer frog after a long fast. The cells are 

 small and almost free from glycogen. The proteid granules are dispersed throughout 

 the cell. 



All the specimens were hardened in 1 p.c. osmic acid, and are drawn to the same 

 or nearly to the same scale. 



glycogen, spending it as fast almost as it is made, but that during 

 the winter a quantity is funded to provide for the demands of 

 late winter and early spring. 



This winter storage of hepatic glycogen in the frog seems 

 closely dependent on temperature. If a winter frog, whose liver 

 is presumably more or less loaded with glycogen, be exposed for 

 some time to a temperature of 20 or a little higher, the liver will 

 afterwards be found to contain little or no glycogen, Fig. 92 B ; 

 and conversely if a summer frog be exposed to untimely cold, 

 glycogen, though not in any great quantity, begins to be stored up 

 in the liver. 



