FLAGELLA. 89 



glass is rimmed with Tarrant's cement or any other good 

 cover-glass cement. 1 



Welch's method : From a pipette, drop glacial acetic acid on 

 the film, allowing it to remain for a few seconds. Pour off 

 the acid (do not wash or wipe it off) and stain with anilin- 

 water gentian-violet. Wash and restain until all the glacial 

 acetic acid has been removed. Then wash in water containing 

 1 or 2 per cent, of sodium chloride. Examine in salt solution. 



FLAGELLA : It is more difficult to stain flagella than 

 either the tubercle bacillus or spores; but it is possible to 

 stain and demonstrate them. 



The method of Loeffler is the best. He uses three solu- 

 tions, Nos. 1, 2, and 3 : 



Solution No. 1. 



20 per cent, solution of tannic acid, 10 grams ; 

 Cold saturated aqueous solution of 



ferrous sulphate, 5 " 



Aqueous or alcoholic solution of 



fuchsin or methyl-violet, 1 gram. 



Solution No. 2. 

 A 1 per cent, solution of caustic soda. 



Solution No. 3. 



An aqueous solution of sulphuric acid of such 

 strength that 1 c.c. will exactly neutralize an 

 equal quantity of caustic soda solution. 



In order to have the flagella show well, the film should be 

 spread as thinly as possible. Mix a small quantity of the 

 culture with a drop of sterile water, and from this mixture 

 take a small portion and spread it on a clean slide or cover- 

 glass. Dry in the air and fix in the flame. Cover the film 

 with solution No. 1 (the mordant) and heat until it begins 

 to steam. Then wash in distilled water followed by absolute 



1 A modification of Johne's method is to wash the film for one minute in 

 a 1 per cent, solution of acetic acid before the stain is applied. 



