178 BACTERIOLOGY 



Stern's Method for the Staining of Spirochete Pallida. 

 The spiral organism discovered in the lesions of syphilis 

 by Schaudinn and Hoffman, and generally regarded as the 

 cause of syphilis, is most easily demonstrated by the 

 following simple method: 



Prepare cover-slips from the serous exudate of the syphi- 

 litic lesion. Allow them to dry, first at ordinary room tem- 

 perature, then for an hour at 37 C. Do not heat over the 

 flame. Immerse them in a 10 per cent, silver nitrate solu- 

 tion in a clear glass dish and expose to diffuse day light (not 

 direct sunlight) for several hours until the films take on a 

 brownish color and a metallic lustre. Then wash in water 

 and mount for examination. The spirochete will be seen 

 as almost black spirals lying in a more or less granular field. 



