60 GENERAL BACTERIOLOGY LESSON 



(d) Float the films on a warm carbol f uchsine solution 

 for two to five minutes. 



(e) Take one of them out, leaving the other in the stain 

 for subsequent examination if necessary. 



(/) Wash it rapidly in water to remove the excess of 

 fuchsine. 



(g) Decolourise it in 25 per cent hydrochloric acid by 

 holding the cover-glass with a pair of forceps and dipping 

 it in the acid just long enough to discharge the red colour. 



(h) Wash it immediately in 60 to 70 per cent spirit : at 

 first the red colour reappears ; continue to wash till no more 

 red comes off. 



(i) Wash it in water to remove the spirit. 





 (k) Dry the film between filter-paper and pass it again 



three times through the flame. 



(I) Now stain it in Loffler's methylene-blue (ten to 

 twenty seconds). 



(m) Wash it once more in water. 



(n) Dry it between filter-paper and again pass it through 

 the flame to dry it. 



(o) Mount it in xylol balsam and examine it with an oil 

 immersion. 



The tubercle bacilli are stained red on a blue ground. 



If no tubercle bacilli be found, the film which was 

 left in the stain should be treated and examined 

 in the same manner. 



It is best to keep the water, acid, spirit, and methylene- 

 blue in wide -necked glass -stoppered pots. Holding the 



