The method detailed below varies little from that described by Warthin and Starry1 for the demonstration of spirochetes in paraffin sections. The only modification has been the substitution of a gelatin film for the capillary space between the two coverslips. Warthin and Starry attached paraffin sections to coverslips, washed them in silver nitrate solution, pressed a second coverslip over the section, and allowed silver nitrate solution to diffuse in between the two coverslips.
When their method was used on a suspected gumma of the brain, it was found that numerous fibers were stained, but none of them could be identified as spirochetes. With the idea of determining the possibilities of the stain in regard to nerve fibers, an investigation was undertaken which resulted in obtaining such preparations as are shown in the illustrations.
One difficulty with the Warthin-Starry coverslip method was the uneven character of the silver deposit. This
FREEMAN W. A SILVER DIFFUSION METHOD FOR STAINING NERVE FIBERS IN PARAFFIN SECTIONS. Arch NeurPsych. 1922;7(3):321-324. doi:10.1001/archneurpsyc.1922.02190090037003