SECRETION. 



183 



fasting condition the chief-cells were large and clear, that during the first six 

 hours of digestion the chief-cells as well as the border-cells increased in size, 

 but that in a second period extending from the sixth to the fifteenth hour, the 

 chief-cells became gradually smaller, while the border-cells renamed large or 

 even increased in size. After the fifteenth hour the chief-cellsxincreased in 

 size, gradually passing back to the fasting condition (see Fig. 81). 



FIG. 81. Glands of the fundus (dog) : A and A 1 , during hunger, resting condition ; B, during the first 

 stage of digestion ; C and D, the second stage of digestion, showing the diminution in the size of the 

 " chief" or central cells (after Heidenhain). 



Langley 1 has succeeded in following the changes in a more satisfactory 

 way by observations made directly upon the living gland. He finds that the 

 chief-cells in the fasting stage are charged with granules, and that during 

 digestion the granules are used up, disappearing first from the base of the 

 cell, which then becomes filled with a non-granular material. Observations 

 similar to those made upon the pancreas demonstrate that these granules 

 represent in all probability a preliminary material from which the gastric 

 enzymes are made during the act of secretion. The granules, therefore, as in 

 the other glands, may be spoken of as zymogen granules, the preliminary 

 material of the pepsin being known as pepsinogen and that of the rennin 

 sometimes as pexinogen. 



1 Journal of Physiology, 1880, vol. iii. p. 269. 



