double membranes separated from each other by an organized hiyer of 

 lipid. This lipid layer constitutes a third membrane, thus giving a three- 

 layered element. Sjostrand also classifies the different membranes as 

 follows: (I) (I cyto-membranes, which are those elements delimiting the 



Figure 3-25. Electron Micrograph of Portion of Mucus-secreting Cell in 

 Olfactory Epithelium of the Frog. The basal surface of the cell is at the bot- 

 tom of the tigure, the free surface at the top. Mucin granules (mg) and 

 mitochondria (m) are visible in the cytoplasm. The parallel arrays of rough- 

 surfaced profiles (er) located in the basal region of the cell represent vertical 

 sections through flattened vesicles or cisternae (500 to 1200 A thick) and are 

 characteristic of the endoplasmic reticulum in this and other protein-secreting 

 cells. The arrays of parallel profiles designated as g represent part of the 

 Golgi complex in these cells. (From Porter, K. R., 1957. "The Submicro- 

 scopic Morphology of the Protoplasm," Harvey Lectures 1955-56, Academic 

 Press, Inc., New York, N. Y.. Fig. 7, Page 184.) 



cisternae; (2) /i cyto-membranes, which are unfoldings of the cell mem- 

 brane into the interior of the cell; and (3) y cyto-membranes, which are 

 smooth-surfaced and generally arranged in parallel as in the Golgi 

 complex. 



Some European workers, including Sjostrand, have suggested re- 

 placing the term, "endoplasmic reticulum" by the term, "ergastoplasm." 



54 / CHAPTER 3 



