THE METHODS OF STAINING MICROBES . 79 



may be stained by the methods of Ehrlich, Ziehl- 

 Neelsen, and Gram. 



The method (devised by Dr. Loftier) for staining 

 the Bacillus diphtherice consists in placing the 

 sections in Loffler's alkaline methylene blue (already 

 described) for about five minutes. The excess of 

 stain is removed by very dilute acetic acid (0'5 per 

 cent). They are then dehydrated in alcohol, clari- 

 fied in cedar oil, and mounted in Canada balsam. 

 Sections may also be stained by Gram's method; 

 and Dr. Klein has produced beautiful stained sec- 

 tions of diphtheritic membranes * by staining them 

 with rubin 2 and methyl blue. By this method the 

 bacilli are stained blue, while the nuclei and necrotic 

 substances of the membranes are stained red. 



To stain the Bacillus typhosus (the microbe of 

 typhoid fever), there are several methods in use. 

 For tissue-staining, the method of Gram may be 

 used. Some bacteriologists recommend steeping 

 the sections for twenty-four hours in methylene 

 blue; but this stain possesses the disadvantage of 

 quickly fading. The colour, however, may be fixed 

 by placing the sections either in a solution of picro- 

 carminate of ammonia, or of iodine dissolved in 

 potassium iodide, or in ammonium picrate. Dr. 

 Kiihne's method consists in allowing the sections to 

 remain for some time in a concentrated aqueous 

 solution of oxalic acid, washing them in water, and 

 afterwards staining with methyl blue dissolved in a 



1 See Report of Medical Officer of the Local Government Board, 

 1889-90, p. 143. 



2 Rubin is rosaniline nitrate. 



