Determination of Refraction Index and Thickness of Histological Sections

Abstract

IN connexion with an investigation into the mechanism of vision of some Arthropoda it was necessary to determine the refractive index, n, of the dioptric tissues of an ommatidium. Owing to the small dimension of these tissues, even in such a big insect as the dragon fly, Aeschna, it would be very difficult to measure this index with ordinary refractometers because the cells in question cannot be separated without damage. Thus n must be determined directly by using histological sections. Due to the fact that cells are never absolutely homogeneous it is possible to determine only an average value of the index. Therefore, the more accurate but circumstantial methods can be replaced by the old and well-known methods of de Chaulnes (1768) if improved in the following way in which only a modern microscope together with a special glass slide device are needed.