704 



PHYSIOLOGY OF DIGESTION AND SECRETION. 



to the glands secreting the gastric juice (gastric secretin or gastric 

 hormone) .* 



Histological Changes in the Gastric Glands during Secretion. 

 The cells of the gastric glands, especially the so-called chief cells, 

 show distinct changes as the result of prolonged activity. Upon 

 preserved specimens, taken from dogs fed at intervals of twenty-four 

 hours, Heidenhain found that in the 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 remained 



Fig. 269. Glands of the fundus (dog) : A and A 1 , during hunger, resting conditipn?; 

 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.) 



large or even increased in size. After the fifteenth hour the chief 

 cells increased in size, gradually passing back to the fasting condition 

 (see Fig. 269). 



Langley * has succeeded in following the changes in a more satis- 

 factory way by observations made directly upon the living gland. 



* See Starling, " Physiology of Secretion," Chicago, 1906, and Edkins, 

 "Journal of Physiology," 1906, xxxiv., 133. 

 t "Journal of Physiology," 3, 269, 1880. 



