144 THE BIOLOGY OF THE FROG chap. 



enormously with the amount of food given and the state 

 of the frog. " If a frog is fed with several worms so that 

 the stomach is much distended with digestible food, the 

 changes are greater and persist for a much longer time. . . . 

 In twenty-four hours the glands, instead of having returned 

 to the hungry state, are still small and consist of somewhat 

 small cells with a more or less distinct inner non-granular 

 border; the lumina are frequently large." The increase in 

 the size of the lumen is accompanied and probably caused 

 by the decrease in the size of the cells. "In frogs to which 

 an excess of food has been given, the non-granular inner 

 zone is usually most obvious about the eighteenth or 

 twentieth hour after feeding. The cells there have increased 

 and are still increasing in size ; the greater clearness with 

 which the non-granular zone can be seen is then probably 

 due to the net increase in the cell granules taking place 

 more slowly than the increase in the cell protoplasm." 



Langley found that the effect of fasting in winter is not 

 very great ; the cells of the gland become somewhat smaller, 

 but they are fairly well filled with granules. If, however, the 

 winter frogs are kept warm, or if frogs at other times of year 

 are kept for a long time in a fasting condition, the cells 

 shrink in size and become clear along the inner border as 

 they do after secretion. 



The mucigen content of the cells lining the mouth of the 

 gastric glands is large in amount before and for some time 

 after a meal, but during the height of the digestive process it 

 becomes much diminished. The changes in the pyloric glands 

 are much like those in the mouth and neck of the cardiac 

 glands. " The maximum amount of mucigen is contained 

 by the pyloric and similar gland cells after a moderately pro- 

 longed fast. The minimum amount of mucigen is contained 

 by these cells twelve to eighteen hours after a heavy meal ; 



