94 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



quickly with fresh and heat again, again removing it when steam 

 rises and allowing the action to go on for fifteen seconds. Do 

 this four times in all, allowing the action to go on for one minute 

 on the last application. Then wash in tap- water or in distilled 

 water with a drop or two of potassium carbonate solution, blot, 

 dry, and mount. 



Another method is to place the slide face downwards in a Petri 

 dish, supported on two slips of glass. The dish is then filled with 

 a mixture prepared as above, and the staining allowed to go on 

 for twelve to twenty hours in the cold, or three to four hours in 

 the incubator, the dish being covered to prevent evaporation. If 

 the slide is inserted face upwards, it will probably be covered by 

 a fine red precipitate. 



The most minute amount of acid is fatal to the process ; hence 

 all instruments must be dry and clean, and distilled water (which 

 often contains traces of acids) should be avoided. 



Examine the film with the -jJj and your highest eye-piece, taking 

 great care to get a good light, white if possible. 



Another method, with which I have been fairly successful, and 

 which is strongly recommended by Herxheimer, consists in 

 fixing as before, and allowing the film to stain for twenty-four 

 hours in a I in i,ooo solution of Nile blue in distilled water. The 

 spirochaetes are stained a fine blue, and are readily recognizable. 



In making the search a good lens and good light are always, 

 and much patience frequently, necessary ; the spirochastes may 

 be but one or two on a film, or there may be several on one field 

 of the microscope. Very occasionally they are matted together 

 in a dense mass. Having found a spirochaete, proceed to see if 

 it resembles the pallida or the refringens ; note especially its 

 length (comparing it with a red blood-corguscle) and the number of 

 turns of which this distance is made up. If there are about six 

 or eight turns to this distance, it is almost certainly pallida ; if 

 there are fewer, it is not. Examine its ends, and see whether they 

 taper off to a point or terminate abruptly. 



It is also possible to see the spirochaete unstained, when it is 

 actively motile, but it is not possible to distinguish it from its 

 congeners in this way without much practice. In point of fact 

 practice is an essential in the diagnosis of syphilis by the recognition 

 of the spirochaete, and the practitioner is recommended to identify 

 the organism as often as he can in undoubted cases before 

 attempting its recognition in doubtful ones for diagnostic purposes. 



