periphery of the cell. The rough-surfaced elements are elongate and 

 arranged more or less parallel to one another. These parallel arrays are 

 interpreted as flattened vesicles of irregular outline and have been termed 



SSi 



Figure 3-23. Electron Micrograph of Basal Portion of Exocrine (acinar) 

 Ceil of Guinea Pig Pancreas. The endoplasmic reticulum consists of parallel 

 rows of vesicles bounded by rough-surfaced membranes and arranged con- 

 centric with the nucleus. Branching of the rows (b) and anastomoses be- 

 tween adjacent rows (a) is shown. Elongated profiles (e) predominate; how- 

 ever, circular (c) and oval (o) profiles are also present in many of the rows. 

 Profiles of the rough-surfaced variety are seen in oblique section (ob) in the 

 upper left corner of the figure. Smooth-surfaced membrane elements (ss^ SS2) 

 are rare in this type of cell and, when present, often occur in small clusters 

 (ssj). The nucleus appears at n and two mitochondria at m. (From Palade, 

 G. E., 1956. "The Endoplasmic Reticulum," J. Biophys. Biochem. CytoL, 

 2, Suppl., Fig. 4, Plate 34.) 



dsternae by Porter and coworkers (Figure 3-25). The cisternae, to- 

 gether with their associated granules, apparently coincide with the baso- 

 philic regions of the cytoplasm and on this basis would correspond to 

 the chromidial substance or ergastoplasm of gland cells first described 

 by Gamier in 1899 (Porter, 1957). 



52 / CHAPTER 3 



