METHOD FOR STAINING FLAGELLA. 141 



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 centimetre 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 propor- 

 tions. 



Of the acid solution : 



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

 For the spirillum rubrum 9 drops. 



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 " 



For other organisms one must determine whether the 

 results are better after the addition of acid or alkali, 

 and how much of either is required. In general it may 

 be said that bacteria which produce acids in the media 

 in which they are growing require the addition of alka- 

 lies to the mordant, while those that produce alkalies 

 require acids to be added. By following Loffler's direc- 

 tions the delicate, hair-like flagellse on motile organisms 

 may be rendered plainly visible. 



There are several points and slight modifications in 

 connection with this method that require to be empha- 

 sized in order to insure success : The solutions should 

 be perfectly fresh ; after mixing the tannic acid, iron, 

 and fuchsin solutions together they should be filtered 

 before using ; when placed on the cover-slip and held 

 over the flame never heat to the boiling-point ; indeed, the 

 best remits are obtained when the preparation is held high 



7* 



