Fig. 7. Pellet of a second postmicrosomal fraction obtained by differential centrifugation 

 (16 hours at 105,000^) from a pancreatic brei (guinea pig) prepared in 0.88 M sucrose. 



The fraction consists of small (~150 A), dense particles which occur either isolated or 

 in chains (arrows) . They are assumed to be the "free" particles of the cytoplasmic matrix. 



Fixation and embedding as for the specimen in figure 4. 



Magnification: 160,000. 



