SYPHILIS 115 



necessary. Full instructions are provided with the apparatus, 

 which can be obtained from the usual agents. 



2. Burn's method is .probably the most suitable for the 

 practitioner who is only occasionally called on to make the 

 diagnosis. The idea is simple and ingenious. The material 

 supposed to contain spirochaetes is mixed with Indian ink, 

 which consists of an emulsion of fine particles of carbon. As 

 the film dries these settle down on each side of the 

 spirochaetes (or any bacteria, etc., which may be present), so 

 that when the specimen is examined microscopically, the light 

 is prevented from passing, except that which goes through 

 the organisms, so that these are seen as transparent bodies 

 on a dark ground. 



The details of the process are as follows : The best ink to 

 use is that sold for the purpose as Burri's ink, or "Pelikan- 

 tusche, No. 541." It can be obtained from any of the agents 

 for Griibler's stains. Shake it well before use, and mix (with 

 a pipette or platinum loop) I part with 4 parts of normal 

 saline solution of water. Take one loopful of the serum from 

 the supposed chancre, etc., and mix it intimately on a clean 

 slide with the same amount of the diluted ink. Spread it out 

 in a thin film, and allow it to dry. Considerable experience is 

 necessary to get the right thickness, and until this is acquired 

 it is a g'ood plan to prepare films which vary greatly in this 

 respect in different parts, some of which will be sure to be 

 about right. When dry apply cedar oil, and examine under 

 the t^-inch immersion lens. Fixation is unnecessary. Pro- 

 targol in 10 per cent, solution may be used instead of Indian 

 ink, and is much better. 



I can strongly recommend this method. It is simple and 

 easy, and very nearly, though not quite, as good as the optical 

 dark background method. For beginners I think it much 

 more trustworthy than any of the staining processes, except 

 perhaps Fontana's method. 



3. Staining Processes. For any of these spread the 

 material obtained as previously described in a very thin layer 

 on a scrupulously clean slide, allow to dry, and fix by gentle 

 heat i.e., such that it does not get uncomfortably hot to the 

 finger. 



Prepare a mixture of 10 c.c. tap-water (or of distilled water 

 4- i drop of a i in 1,000 solution of potassium carbonate) and 



