To use this section, click on one of the primals on the picture on the left side of the screen. A picture will appear of that primal.  Click on one of the individually lettered sections of that primal. A photograph and a drawing will be shown in the window on the right side of the screen. In order to switch from photograph to drawing, click on the emblem in the lower right hand corner of the picture. You will then be able to click on individual muscles and a description will show up in a new window.