A silver impregnation technique for normal axons in the human central nervous system for celloidin and epon sections, with substitutes for soft tap water

An improved silver technique has been developed for human CNS axons in sections from celloidin blocks that resist impregnation because of prolonged storage in alcohol. This method also gives consistently good impregnation of recently fixed material, and thus is suitable for routine use. Slightly modified, the method is also successful with osmicated Epon embedded sections. The quality of silver impregnation in methods using tap water in the reducing solutions varies in different laboratories. Having established that hard water is essential, substitutes for soft water were sought and found.