The retina is a part of the central nervous system, and its neurons are supported by an elaborate system of glia, as are neurons in general. The supporting system of the brain contains three types of elements: the astroglia, the oligodendroglia, and the microglia; in the brain we possess a solid knowledge of all three types of cells. In the human retina, on the contrary, with the exception of the cells of Müller (radial fibers), not much is known of the glia. Friedenwald1 stated that "unfortunately, few extensive studies have been made on the retina with special stains developed in the past 20 or 30 years to demonstrate neuroglia and microglia." This gap in our knowledge is due to technical difficulties, since with the conventional histologic procedures or the older metallic impregnations it is not possible to visualize the glia. However, some of these difficulties were recently alleviated by