Silver ion is not specific either in location or in action in the present silver method. Studies with radioactive silver, with the dark-field microscope, and with simple reducing solutions demonstrate a general distribution of silver ion in the impregnated tissue. Copper and mercury may be substituted for silver in the impregnating solution. A water-soluble aldehyde is necessary as a fixative. The substrate for staining appears to require the presence of protein-bound amine groups. The product-forming solution does not require the presence of a reducing agent. Sulfite ion is not necessary. All controllable sources of base that were utilized produced the histologic results. The product appears to be silver oxide in terms of the present solubility studies.