Appendix. Neurofibrillar staining of cat retinae

Previous work on the staining of mammalian retinae by neurofibrillar methods has been reviewed in Wässle et al. (1978). The emphasis there was on the quantitative staining of A-type horizontal cells. The procedure described below is essentially that of Gros-Schultze (Romeis 1968) combined with modifications taken from Nauta & Gygax (I951) and guided by Richardso's (1960) valuable discussion. Our requirement was to be able to stain any cat retina reliably and to pick out the alpha cells quantitatively. It took some time to evolve a consistent procedure; hence, although not particularly original, we report in detail what was done. We were unable to use Holmes silver-staining with retinae attached to the slide as described here but Bodian's method could be used. Attachment to a slide proved to be essential for quantitative and regular staining (e. g. microscopic control during the staining) and because shrinkage was minimized and thus the background was less dark. The detailed quality of the staining with respect to alpha cells is discussed in the next paper.