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 hght (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. 



