BACILLUS OF SYPHILIS. 213 



with an aqueous solution of sulphurous acid. Wash in water, 

 return to the permanganate solution for a few seconds, and 

 then place in the sulphurous acid again until the film is thor- 

 oughly decolorized. It is dehydrated in alcohol, cleared in 

 oil of cloves, and mounted in Canada balsam. Nitric acid 

 readily decolorizes the syphilis bacillus, but not the tubercle 

 or lepra bacilli. 



Van Niesen cultivated a bacillus about the size of the 

 tubercle bacillus from the blood of a number of cases of 

 syphilis. The blood is obtained by puncture from the finger, 

 and kept in a sterile dish at a temperature of 13 to 15 C. 



FIG. 88. 



X 



Syphilis bacilli from a papule, after a preparation from Lustgarten. X 2500. 



for ten days. It is then ready to be transplanted. In bouil- 

 lon this bacillus produces grayish-white threads; some of them 

 forming a membrane on the surface and others floating in the 

 medium. In a gelatin stroke culture it forms a fine grayish, 

 streaky-looking mass, which consists of threads, some of which 

 penetrate into the medium. The gelatin is liquefied very 

 slowly. The growth on agar consists of a central grayish 

 mass with projecting rays. Potato, milk, urine, serum, and 

 water are also available as culture-media. 



The colonies in the plate culture are quite characteristic, 

 turning from gray to yellow, and finally to brown. The 



