150 BACTERIOLOGY. 



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 centimetre will be exactly 

 neutralized by one cubic centimetre of the alkaline so- 

 lution. 



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 . . . % 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 oadema . . . 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 Loeffler's direc- 

 tions the delicate, hair-like flagellaB 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 culture to be em- 

 ployed should be young, not over 18-20 hours old. It 

 should have developed for this time on fresh agar-agar at 



