go BACTERIOLOGICAL DIAGNOSIS. 



Having obtained a clear view of the bacilli examine 

 them for motility and absence of clumps, and see whether 

 they are present in proper proportion to the amount of 

 fluid. 



If the culture is in good condition the bacilli should 

 be seen darting about in all directions, but if the move- 

 ment is but sluggish the reaction may still be obtained. 

 If the specimen is kept for a short time in a warm 

 place or in the incubator the movements will usually 

 become more rapid. It is hardly necessary to say that 

 when dead cultures are used there will be no move- 

 ments of translation, though the bacilli may show 

 oscillatory (Brownian) movements. 



The specimen must be searched thoroughly for clumps 

 of bacilli, and if these are present the emulsion must be 

 filtered through a double thickness of white filter paper. 

 This examination for clumps is a most important part 

 of the process, and must be attended to whether dead 

 or living cultures are in use. 



Next see that the emulsion is neither too thin nor 

 too thick. No definite rules can be given, but if there 

 are very few bacilli in the field a further supply of 

 growth must be added to the stock of emulsion, and a 

 further specimen examined. If the bacilli are thickly 

 crowded together the emulsion must be diluted with a 

 little water and re-examined. 



When you are satisfied that the emulsion is right, 

 slide off the cover-glass and drop it into some antiseptic 

 lotion ; of course this is unnecessary if dead cultures 

 are used. 



2. Making the dilution. You are now about to dilute 

 a drop of the serum from the patient with a known 

 multiple (in this case thirty times) of its bulk of the 

 emulsion which you have just prepared. To do so you 



