Some experimental observations on the retina of the gecko

Abstract

The association of visual purple or rhodopsin with the visual function of the rods in dim or twilight vision as maintained in the duplicity theory of von Kries (Nagel,1 Helmholtz,2 Parsons,3 and Hartridge4) is generally regarded as well substantiated.As to the genesis of this pigment, numerous ideas have been advanced, although it is generally held that it is a product of the epithelial pigment cell (Garten5 and Kolmer6).In the present work on the gecko retina, which is cone-free, certain observations have been made which suggest that the outer segment of the rod may be more directly concerned in the production of this pigment.When the retina is preserved in modified Held's fixative (v. Kolmer, op. cit.) and stained with iron haematoxylin and erythrosin, numerous droplets, which stain with a varying intensity from gray to black, are seen on and between the outer segments of the rods. In addition, a characteristic lamellar arrangement of deeply staining granular material in the outer segment of the rod is ...