PATHOGENIC BACTERIA. 95 



Canada balsam. Examined with oil-immersion. The tubercle 

 bacilli red, all else blue. 



Slow Method. When perfect permanent preparations are 

 desired and the bacilli to be seen unaltered, the slow method is 

 to be preferred, and it is to be recommended whenever the time 

 allows. It consists simply in allowing the carbol-fuchsin to work 

 upon the preparation a number of hours. We usually place th- 

 cover glass with the dried sputum and which has been drawn 

 through the flame three times, in a little dish containing enough 

 dye to allow the glass to be immersed. We do this about 5 or 6 

 o'clock P.M., and the next morning the preparation is ready 

 for decolorizing, the process being the same as described above, 

 viz., 25$ nitric acid, alcohol and water, and the contrast stain 

 methylin blue. We thus avoid the formation of ugly crusts, 

 the bacilli are not distorted, the specimen is permanent and 

 very clear. 



Biederfs Method of Collecting Bacilli, when the baci-lli are 

 very few in a great quantity of fluid, as urine, pus, abundant 

 mucus, etc., Biedert advises to mix 15 c.cm. of the fluid 

 with 75 to 100 c.cm. water and a few drops of potassium or 

 sodium hydrate, then boiling until the solution is quite thin. It 

 is placed in a conical glass for two days, and bacilli with other 

 morphological elements sink to the bottom of the glass ; when 

 the supernatant liquid is decanted, the residue can be easily 

 examined. In this way bacilli were found that had eluded 

 detection examined in the ordinary manner. 



The centrifugal machine is used either in connection with 

 Biedert's sediment method or without, to obtain the solids sus- 

 pended in urine or serum. 



Without cover-glass. Sputum can be spread and stained on 

 the glass slide without the use of a cover-glass, the oil 01 cedar 

 being placed directly on the stained sputum, and the oil immer- 

 sion lens dipping into it. It is a rapid and cheap way ; and 

 when a given case is to be studied daily the method is useful. 



Pure Cultures from Sputum. Kitasato recommends the tho- 

 rough washing, changing the water ten times, of the small masses 

 found in the sputum of tubercular persons. When such speci- 

 mens are examined they show tubercle bacilli alone, and when 

 inoculated in agar give rise to pure cultures. 



