SPECIAL METHODS OF STAINING BACTERIA. 163 



brown, again washed out for a few seconds in alcohol, 

 and finally for one-fourth minute in absolute alcohol. 

 From this they are transferred to xylol for a half- 

 minute. ' The remaining steps in the process are the 

 same as those given in the general method. In some 

 cases better results are obtained by reversing the steps 

 in the process and staining the bacteria last, for then 

 the frequent decolorizing action of the alcohol on the 

 bacteria is diminished ; thus, place the sections from 

 alcohol into eosin, safranin or Bismarck-brown for a few 

 minutes, then wash out in 50 per cent, alcohol, then for 

 from three to five minutes in the dilute aniline-water 

 gentian-violet solution, then into the iodine bath, after 

 three minutes wash out in alcohol, and, finally, for one- 

 fourth minute in absolute alcohol, and then into the 

 xylol, from which they may be mounted. Some of the 

 organisms which may be stained by this method are 

 micrococcus tetragenus, b. diphtherice, b. anthrads, and 

 staph. pyogenes aureus. It cannot be successfully em- 

 ployed with the bacillus of typhoid fever. 



Staining with dahlia and decolorizing with sodium carbo- 

 nate solution. Another method that is not very commonly 

 employed, though the results obtained by its use are in 

 many cases very satisfactory, is to stain the tissues in a 

 strong watery solution of dahlia (about one-fourth satu- 

 rated) for from ten to fifteen minutes ; from this they 

 are transferred into a 2 per cent, solution of sodium or 

 potassium carbonate, and from this into alcohol, alter- 

 nating from the one to the other, until the section is 

 almost colorless. From the alcohol they are rinsed out 

 in water and then put into a dilute watery solution 

 of either eosin, Bismarck-brown, or safraniu for one 

 minute, then washed out in alcohol, finally in absolute 



