Application of histochemistry to electron microscopy

In order to use histochemical methods in corn-bination with electron microscopy for the study of the function and the fine structure of cells, we have proceeded along certain lines as working hypotheses. Our main assumption is that a com-promise should be made between the distinct requirements of histochemistry and of electron microscopy. It would seem at first hand that the requirements of these disciplines are mutually antagonistic; but, if we have done anything with our investigations, it is to indicate that this is not so, especially in our selected circumstances. It may be effective, therefore, to review some of the separate requirements from which compro-mises must be made. For electron microscopy one of the most exact-ing requirements concerns the adequate preser-vation of the fine structure of cells by fixation. At present there are few fixatives which give satisfactory results. Among the chief ones that have been used, (osmium tetroxicle (15), potas-sium dichromate (6), potassium permanganate (12), and formalin (17)) osmium tetroxide and the permanganate are considered the best be-cause they preserve the membranous strut-tures of the cytoplasm. The other two fixatives, which have been extensively used in light microscopy, are less adequate because they do not preserve the extensive intracellular mem-branous systems. They have been employed, though, for the fixation of structures (nuclei, various granules, etc.) which consist primarily of concentrated proteins. It should he pointed out that the use of formalin, in particular, has indicated that the distribution of densities in Presented as the 5th paper in the Gomori Symposium: “Localization in Histochemistry.” at the 8th annual meeting of the Histochemica