==History== [[Image:Frog_ganglion_cells.jpeg|thumb|right|200px|Cajal's drawing of ganglion cells of the frog retina <ref name="Kolb">Kolb, Helga, Nelson, Ralph, Fernandez, Eduardo, Jones, Bryan, The Organization of the Retina and Visual System, Simple Anatomy of the Retina. url=http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/</ref>]] [[File:Dog and ox ganglion cells.jpeg|thumb|right|200px| Cajal's drawing of ganglion cells of ox and dog retinas ]]