METHOD FOR STAINING FLAGBLL^. 137 



Tannic acid solution in water (20 acid, 80 



water) .10 c.c. 



Cold saturated solution of ferro-sulphate . 5 c.c. 



Saturated watery or alcoholic solution of 



fuchsin 1 c.c. 



This solution represents the mordant. A few drops 

 of it are to be placed upon the film of bacteria on the 

 cover-slip, which is then to be held over the flame until 

 the solution begins to steam. It should not be boiled. 

 After steaming, the mordant is washed off in water and 

 finally in alcohol. The bacteria are to be stained in a 

 saturated aniline-water fuchsin solution. 



When treated in this way different bacteria behave 

 differently: the flagellse of some stain readily in the 

 above solutions ; others require the addition of an alkali 

 in varying quantities ; while others stain best after the 

 addition of acids. To meet these conditions an exact 

 1 per cent, solution of caustic soda in water must be 

 prepared, and also a solution of sulphuric acid in water 

 of such strength that one cubic centimentre will be 

 exactly neutralized by one cubic centimetre of the 

 alkaline solution. 



For different bacteria which have been studied by this 

 method, the one or the other of these solutions is to be 

 added to the mordant in the following proportions. 



Of the acid solution : 



For the bacillus of Asiatic cholera . . J to 1 drop. 

 For the spirillum rubrum . . .9 di-ops. 



Of the alkaline solution : 



For the bacillus of typhoid fever . . 1 c.c. 



For the bacillus subtilis . . . 28 to 30 drops. 



For the bacillus of malignant oedema . 36 to 37 " 



