Plate 10 



A. Portion of cytoplasm of a rat pancreas cell. A typical secreting cell 

 (p. 110). R, reticulum of particle covered membranes; P, are RNP 

 particles; M, cell membranes; m, mitochondrion. 



B. Microsomes from rat liver cells homogenized and fractionated by 

 centrifugation. Note many small, particle-covered vesicles derived from 

 the break-up of more extensively-developed, particle-covered membranes 

 in the original cells. V, vesicles, and P, particles. 



Micrographs kindly supplied by M. S. C. Birbeck. 



