Microhic Diseases Individually Considered. 227 



the action of strong acids — nitric and sulphuric ; upon 

 this property are based the diiferent methods of double 

 staining which we will now describe. This property 

 is also possessed by the bacillus of leprosy. 



1. Ehrlich's method. 



The staining fluid is composed as follows : 



Aniline water (1) . . . . 9 cub. cent. 

 Absolute alcohol . . . . 1 cub. cent. 



• Concentrated alcoholic solution of 

 fuchsin, methyl violet, or gentian 

 violet . . . . . .1 cub. cent. 



Cover glasses remain in this solution half an hour 

 at least, sections twenty-four hours. 



Decoloration is obtained by a dilution of nitric 

 acid — 1 part nitric acid in 5 parts distilled water or in 

 10 parts alcohol. Cover glasses or sections should re- 

 main in the decolorizing fluid only from half a min- 

 ute to a minute. They are then washed in distilled 

 water and mounted. If it is desired to stain the 

 background of the specimen so as to render the color 

 of the bacilli more distinct, the preparations, after 

 coming from the distilled water, are placed in a hydro- 

 alcoholic solution of methylene blue if fuchsin has 

 been the first stain, or in eosin, safranin, bismark brown, 

 etc., if the bacilli have been stained violet ; then they 

 are mounted. 



The time required by this method may be abridged 

 by raising the temperature of the staining fluid to 



(1) Aniline water is made in the following manner: A drop of 

 aniline oil is added to a few cubic centimeters of distilled water in a 

 test tube ; the tube is vigorously shaken in order to dissolve the 

 oil, and a few drops of absolute alcohol added to complete this 

 solution. 



