THE STAINING OF BACTERIA. 49 



ized, until all blue coloring visible to the naked eye has dis- 

 appeared, in the following solution : 



Alcohol (80 per cent.), 98 parts ; 



Nitric acid, 2 " . 



The cover-glass is then dipped for a few seconds into the fol- 

 lowing solution : 



Saturated alcoholic solution of eosin, 10 parts ; 

 Water, 90 '" . 



After this it is again rinsed in water, dried, and mounted. 



The Second Method. 



Float a cover-glass preparation film-side down in a watch- 

 glass full of Koch-Ehrlich's fuchsin solution. Take the watch- 

 glass by its edge with a pair of forceps and hold same over 

 a low Bunsen flame until the staining fluid begins to boil. 

 Remove from the burner, and after a few minutes repeat this 

 process five or six times. After cooling, the cover-glass, 

 without washing in water, is transferred to a second watch- 

 glass containing a decolorizing solution as follows : 



Absolute alcohol, 100 parts ; 



Hydrochloric acid, 3 " 



Place the cover-glass, film-side up, at the bottom of this 

 watch-glass and let it remain for one or two minutes. 

 Remove, wash in water, stain with methylene-blue solution 

 for one or two minutes, wash rapidly in water, dry, and 

 mount. 



By this method the spores will be stained red and the body of 

 the bacteria cells blue. 



The Third Method. 



Cover-glasses are prepared in the usual way. After fix- 

 ing, the preparation is immersed in chloroform for two min- 

 utes, washed in water, placed for one or two minutes in a 5 

 4 M. B. 



