During the last five years a number of important articles dealing with the location of spirochetes in general paralysis have appeared, especially in the German literature, and I wish to try to summarize briefly the main facts, comments and theories that have resulted from the studies of three of the best investigators, namely, Jahnel,1 Sioli2 and Hauptmann.3
Jahnel4 of Frankfurt has devised an excellent silver stain for spirochetes in the central nervous system. This stain brings out the organisms with great sharpness on a yellow, or yellowish-brown background; it usually leaves unstained those elements of nervous tissue (axis cylinders, etc.) that have heretofore been so troublesome to all who have tried to study spirochetes. It is largely due to the excellence of this stain that others, besides Jahnel himself, have been stimulated of late years to study the position, the distribution and the activity of these