Figure 199 from Chapter 6 (Golgi Apparatus) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. The Golgi apparatus in epithelial cells from the mouse epididymis. The convex, or cis, side of the Golgi shows selective deposition of osmium, whereas the concave, or trans, side is resistant to osmium staining even after long periods of postosmication. Tissue shown here was prepared with collidine-buffered osmium fixation followed by 40 hours postosmication at 37° C. Image by Daniel Friend. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.