190 BACTERIOLOGY. 



paper is used for filtering the mordant, and there should 

 be left a heavy precipitate. After filtering, the color 

 of this mordant should be of a reddish-brown hue, not 

 clear, but somewhat cloudy, and this mordant must be 

 used within five hours after it is made. After that time 

 it loses its fixing power. This is indicated by its 

 gradual clarification and darkened color. It gives the 

 best results when strictly fresh, and accomplishes its 

 work in a much shorter time, so that very little if any 

 heating is required when it is placed on the cover-glass 

 preparation. 



Carbol-fuchvin Stain. Take about 1 gramme of 

 granulated fuchsin (not the acid fuchsin), put it in a 

 bottle, and pour over it about 25 c.c. of warm absolute 

 alcohol. Shake vigorously and let it stand for several 

 hours before using. The carbol-fuchsin is made by 

 diluting the saturated alcoholic solution four or five 

 times with a 5 per cent, solution of carbolic acid. Car- 

 bol-fuchsin should be freshly made, heated, and filtered 

 before using. 



The application of this method of demonstrating the 

 flagella varies with different organisms with regard to 

 the length of time the mordant and stain are allowed to 

 act, and the amount of sodium hydroxide solution used. 

 Usually, it is well to heat the mordant on the cover-slip 

 to steaming, and allow it to act from one-half to one 

 minute. It is then washed off with water and a small 

 quantity of alcohol poured over the surface and washed 

 off instantly. The water on the cover-slip is now 

 absorbed from the edge of the cover-slip with clean 

 filter-paper. The carbol-fuchsin stain is now applied 

 and heated just enough to generate a thin vapor. The 

 stain should not act for more than from one-half to one 



