COLORING AGENTS. 59 



of Ehrlich and Koch are also well-known in con- 

 nection with the further improvement of this 

 method of research. 



In the following paragraphs only some of the 

 most useful aniline dyes will be mentioned ; their 

 number is daily increasing. In general it may be 

 stated, that all preparations stained by aniline 

 colors should be carefully washed before being 

 mounted ; they must also be kept in the dark, as 

 most of "these colors soon fade in the light. 



FUCHSIN, 



In an alcoholic tincture, colors especially well thick- 

 ened cell-walls ; the different layers often with dif- 

 ferent intensity. Sections which are to be stained 

 should be free from potash, which destroys the 

 color, and they must be treated in alcohol, the addi- 

 tion of water precipitating the dye. Stained prepa- 

 rations remain unchanged only for a limited time. 

 Fuchsin has recently been applied by Ehrlich ' 

 similarly to vesuvin, with methylene blue, for the 

 staining of the Bacillus of tuberculosis. 



HANSTEIN'S ANILINE VIOLET 



Is prepared by mixing about equal parts of methyl 

 violet and fuchsin, and dissolving them in alcohol. 

 Its action depends upon the different avidity of 



1 Ehrlich: Zeitschr. f. klin. Medicin, 1882, IL 



