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PLATE XI. Endoplasmic reticulum of a pancreatic acinar cell (guinea pig) showing newly formed 

 proteins collecting in granules (g) in the network of tubules leading eventually to the cell membrane. 

 The dense ribosomal particles (r), sites of protein synthesis, are found in the cytoplasmic matrix and 

 on the membranes of the endoplasmic reticulum. 40,000 X- (Courfesy of G. E. Palade.) 



