378 



FOOD AND DIGESTION 



blance in structure to the salivary glands. Its capsule and septa, as well as 

 the blood vessels and lymphatics, are similarly distributed. It is, however, 

 looser, the lobes and lobules being less compactly arranged. 



Heidenhain has observed that the alveolar cells in the pancreas of a fast- 

 ing dog consist of two zones, an inner or central zone which is finely granular, 

 .and which stains feebly, and a smaller parietal zone of finely striated proto- 



FIG. 267. Duct with Laterals to the Alveoli. Silver method of Golgi (E. Muller). A 

 Duct with branches; m, between the cells. B, Laterals more strongly magnified. 



plasm which stains easily. The nucleus is partly in one, partly in the other 

 zone. During secretion it is found that the outer zone increases in size, and 

 the central granular zone diminishes, as in the case of the salivary glands. 

 The pancreatic cell itself becomes smaller from the discharge of the secretion. 

 During a period of rest the granular zone again increases in size and the 

 outlines of the cells become full and indistinct. The granules, as in the sali- 

 vary cells, are the material from which, under certain conditions, the fer- 

 ments of the gland are developed, and which are therefore a zymogen. In 

 addition to the ordinary alveoli of the pancreas there are distributed irregu- 



