FLAGELLA. 91 



Tannic acid, 1 gram ; 



Distilled water, 10 c.c. 



The cover glass is spread with a very thin film, dried, and 

 fixed. Cover with the mixed solution and heat almost to 

 boiling. Wash in water until the glass is clean, dry, and 

 mount in Canada balsam. 



Muir has modified this method by using two solutions, a 

 mordant and a stain : 



Mordant. 



Tannic acid (10 per cent, aqueous 



solution, filtered), 10 c.c. ; 



Corrosive sublimate (saturated aqueous 



solution), 5 " 



Alum (saturated aqueous solution), 5 " 



Carbol-fuchsin, 5 " 



Mix well, and after the sediment has settled the super- 

 natant clear fluid is pipetted into a clean glass-stop- 

 pered bottle. 



Stain. 



Alum (saturated aqueous solution), 10 c.c. ; 



Gentian-violet (saturated aqueous solu- 

 tion), 2 " 



This stain may be substituted for the carbol-fuchsin in the 

 mordant. Cover the film with the mordant solution and 

 heat until steam arises. Wash in running water for two 

 minutes. Dry carefully over a flame and stain, heating as 

 before. Wash in water, dry, and mount in a drop of xylol 

 balsam. 



L. Smith stains the flagella with night-blue. The method 

 is simple. He advises, however, that only young cultures be 

 used. The cover-glass must be clean and free from fatty 

 matter. Mix 1 gram of potassium alum with 40 c.c. of dis- 

 tilled water and place in the incubator over night. Dissolve 

 5 grams of night-blue in 20 c.c. of absolute alcohol and mix 

 with the first solution. Filter until the filtrate comes through 



