Methods of Impregnating Neurofibrillar Substance on Slides After Imbedding

Abstract

This paper describes three new methods for impregnating neurofibrillar substance in sections prepared from imbedded material and then mounted on slides. The first two methods are simpler than any previous slide methods for, after the silver bath, the usual reduction is left out and the silver is replaced directly by gold. All these methods can be modified to some extent for selective impregnation of connective tissue fibres (Fig. 4) simply by adding two drops of concentrated ammonia per 100 ml. to the colloidal silver bath, but a discussion of the impregnation of the connective tissue fibres is not included in this paper.I. Direct Albumen (Silver-Gold) Method By using 0-2 to 0-5% egg albumen and 2% silver nitrate in aqueous solution (a colloidal silver bath) it is possible to impregnate the neurofibrillar substance of the central nervous system on slides of imbedded and sectioned materials fixed in a variety of ways. The slides are kept in the silver colloid bath for five days at 370 C. or for eight days at room temperature, then gilded for 10 minutes by dropping 022% aqueous gold chloride solution onto the slides, and subsequently reduced in a 0 2% aqueous oxalic acid solution for an hour. Between the steps of the technique, especially between the silver colloid and gold, the slides have to be well washed with distilled water.This method is extremely simple: over-or underimpregnation or reduction is impossible; the results are selective, free of precipitate, and constant; it works even after decalcification of the material to be impregnated by trichloro-acetic acid.Fixation.