STAINING OF FLAGELLA 93 



the preparation is spoiled, as a fine precipitate of mordant 

 is produced, which becomes stained later on and obscures 

 flagella. 



The heating must only last for from half to one minute ; 

 the liquid is poured off, and the cover-glass thoroughly 

 washed with water ; it is allowed to dry in the ordinary 

 way. The preparation is then stained with a few drops of 

 5 per cent, aniline-water solution of fuchsine. The cover- 

 glass may be gently warmed for about a minute, after 

 which the stain is washed off very thoroughly with water ; 

 the cover-glass is now air-dried and mounted in balsam. 



If the preparation is a successful one, the bacteria are of 

 a very dark-red colour, and much thicker than when stained 

 by the usual methods. In the ordinary processes of stain- 

 ing, only the protoplasmic body of the organism is coloured, 

 the outer sheath-like covering but rarely taking up any 

 dye at all ; the above process, however, stains both the 

 cell-wall and the protoplasmic contents, thus making the 

 organism appear thicker than when stained in the ordinary 

 manner. The flagella should be seen as a number of very 

 fine curved threads, stretching out in an irregular manner 

 from the bacilli, more or less intensely stained. 



Van Erinengem's Method. — This method is easy, and gives 

 good results in careful hands. The following solutions are 

 prepared : 



(a) Osmic acid (2 per cent, solution), 1 part. 

 Tannin (10 to 25 per cent, solution), 2 parts. 



To each 100 c.c. of the tannin solution add 4 or 5 

 drops of acetic acid (glacial). 



(b) Nitrate of silver (-25 to "5 per cent, solution). 



(c) Gallic acid, 5 grammes. 

 Tannin, 3 grammes. 



Fused acetate of soda, 10 grammes. 

 Distilled water, 350 grammes. 



