FUNCTIONAL CHANGES IN STRUCTURE 



77 



Fig. 7. Guinea pig fed after a fast of 4S hours. Pancreas fixed 1 hour after beginning of 

 meal. The micrograph shows a limited field at the periphery of the centrosphere region. Rough- 

 surfaced elements (rs) of the endoplasmic reticulum can be seen along the upper margin of the 

 figure. Smooth-surfaced vesicles (ssi) and stacked cistcrnae (sS'^) together with large vacuoles 

 (/■i — rr,) of irregular shape occupy the centrosphere region. These vacuoles an- p.ulially tilKd 

 with masses of dense material similar in density and texture to the content of the zymogen 

 granules (zi, 0-). It is assumed that they represent successive stages in a hlling process that ends 

 with the formation of mature zymogen granules. X 37)000 



