Chap, iv.] METABOLIC PROCESSES OF THE BODY. 



565 



the various forms of carbohydrates, or with proteids, or with 

 other substances, is of the same kind and presents the same 

 characters ; at least we have no evidence to the contrary. 



The storing-up of glycogen in the liver is also influenced 

 by other circumstances than the taking of food. For instance 

 in the frog an increase of glycogen takes place during the win- 

 ter months. In the summer months the liver of a frog will be 

 found to contain very little glycogen, Fig. 106 C, unless the 

 animal has been unusually well fed; whereas a liver examined in 

 mid winter, Figs. 105, 106 A, will be found to contain a consider- 

 able quantity, even though no food has been taken for months. 

 In such a case the material for the formation of the glycogen 

 in the liver must have been furnished by some part of the body 

 of the frog, and could not, as may be the case when a meal 

 leads immediately to an increase of glycogen, be supplied 



B 



Fig. 106. 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 considerable 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 pro- 

 teids 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. 



