718 



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 or THE HEPATIC CELLS OF THE Finn;. (Langley.) 



A. Cells rich in glycogcu. 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 glycogeu 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. 



