Colour of Red Blood Corpuscles

Abstract

A SINGLE red blood corpuscle, illuminated by white light, appears yellow under the microscope. Why does it not appear pink? I have asked distinguished zoologists, physiologists, histologists and authorities on colour-vision, but only one has given even a tentative answer, though all have agreed to the fact. The yellow appearance is mentioned by the authors of a few histological text-books, but they either make no comment or else suggest that one would expect yellowness on account of the thinness of the coloured layer. The change of colour of certain dyes, on dilution is sometimes attributed to different degrees of dissociation of the dye molecule, but the yellow appearance of a single red blood corpuscle must clearly be attributed to some special phenomenon of colour-vision that is not a matter of general knowledge among biologists.