Differential Impregnation of Degenerating Nerve Fibers in Paraffin-Embedded Material

The silver method of Nauta and Gygax (1951) has been used on paraffin embedded material to give a result closely comparable to that obtained by Nauta and Gygax (1954) on frozen sections. It has been found that pyridine plays an important part in suppressing the impregnation of normal fibers in paraffin embedded material and that this sup pression can be augmented by the use of some of the higher methylated derivatives of pyridine, particularly 2,4,6-trimethyl pyridine (collidine).