Figure 191 from Chapter 5 (Endoplasmic Reticulum) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A thin section through frog sartorius muscle shows the organization of the sarcoplasmic reticulum in amphibians. The components of the reticulum are evident in the verticle strip in the center of the micrograph; the two flanking strips are myofibrils. The myofibril on the right is slightly out of register for technical reasons. Image by Lee Peachy. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.