Abstract
Using active glyceroldichlorohydrine and fluorescence-microscope, vitamin A, rhodopsin and fat in the retina were observed histochemically. (1) Irrespective of light- or dark-adaptation, vitamin A is always found in the pigment epithelial cells of the retina of carps, rats and bats, where rhodopsin is seen only at dark adaptation. Vitamin A is not found in chicks and love-birds in whom rhodopsin fails. In chicks and love-birds, coloured fat drops are seen at light adaptation and they increase considerably at dark adaptation. (2) Vitamin A in the outer segments of the rods is used for formation of rhodopsin. Riboflavin also participates in this process. (3) The shorter the wave-length of light, the stronger the effect of changing rhodopsin into vitamin A. (4) The amount of vitamin A needed for the formation of rhodopsin varies according to the species of animals and of vitamin A. (5) Generally speaking fat is found in a larger amount during light-adaptation, but it varies in different animals. (6) The distribution of vitamin A does not always run parallel with the quantity of fat.
