Optical activity and the fixation of rods and cones.

Abstract

VERTEBRATE rod outer segments have been known for more than a century to rotate the plane of polarization of transmitted light1. When the polarizer in the path of a beam illuminating a microscope stage points north, and the analyser crosses it, suspensions of fresh bleached rods and cones obtained from the retinae of the frog (Rana esculenta), cat, rabbit and goldfish severally show that the receptors pointing along a NW axis maximally transmit light independently of the colour of the illuminant. Some of the conditions which effect a switch of the axis of maximum transmission through 90° have been discussed by Schmidt1, an extension of whose work is now under way (unpublished results of G. M. Villermet and myself), and has been briefly reported2. This preliminary report draws attention to the differential action of two fixatives, namely formaldehyde and glutaraldehyde.