356 R. R. BENSLEY 



zone of small granules of irregular shape, which I regard as 

 zymogen granules in process of formation, and therefore call 

 prozymogen granules. These must not be confused with the 

 basophile substance of the cell which has elsewhere been called 

 ' prozymogen' by Macallum and myself. 



When stained with neutral red and examined fresh in salt 

 solution the basal zone remains quite unstained. The zymogen 

 granules stain faintly red in dilute solutions, but may be made to 

 stain strongly by using stronger solutions of the dye. Resting 

 acini show a clear basal zone which is unstained, and a distal zone 

 containing coarse zymogen granules which are faintly stained. 

 In the active gland, as for example, after a few hours' secretin 

 stimulation, or after a meal, a new element makes its appearance, 

 between the zymogen granules, which are now reduced in number 

 and size, and the basal clear zone. These are the prozymogen 

 granules referred to in the preceding paragraph. They are par- 

 ticularly conspicuous in the preparations stained with neutral 

 red because they stain much more intensely than the zymogen 

 granules. After prolonged secretion, the zymogen granules have 

 wholly disappeared and the secretory content of the cells is re- 

 duced to a narrow row of these prozymogen granules along the 

 lumen. If the stimulation is continued long enough even these 

 disappear. I regard these granules as J^oung zymogen granules 

 for the reason that they wholly disappear from the pancreatic 

 cells after a sufficient period of rest, while a few hours' stimulation 

 will cause their reappearance in the usual situation. 



In preparations stained in dilute solutions of janus green, as 

 was first pointed out by Michaelis ('00), there appear in the basal 

 zone, distinctly stained, the structures which were responsible for 

 the faint striation observed by Heidenhain. These structures 

 are, as Michaelis recognized, identical with the elementary fila- 

 ments described by Altmann ('94) in the pancreatic cell, but as 

 Michaelis also correctly recognized, have nothing to do with the 

 structures which have been variously termed basal filaments, 

 ergastoplasma, etc. In the janus green preparations these ele- 

 ments may be seen as independent rods or filaments resembling 

 bacilli, located for the most part in the basal portion of the cell. 



