GEKEKAL METHODS. 



WITH ANILINE VIOLETS. 



It would appear that the first application of Aniline colours 

 to Bacteriological investigation was due to Weigert, who 

 stained in a simple aqueous solution of Methyl Yiolet. 



To better fix the colouring matter, Erhlich used a saturated 

 solution of Aniline in Water as a mordant for the dye, the 

 dye being dissolved in this, or added in the form of a con- 

 centrated alcoholic solution till a slight opacity appears. 



Weigert subsequently proposed definite volumes of the solu- 

 tions which have been generally adopted, with the further 

 addition (by Koch) of 10 per cent, of Absolute Alcohol to 

 make a more permanent solution. Koch states that the solu- 

 tion so made will remain good for 10 days, without requiring 

 to be filtered each time of using. Weigert later substituted 

 Gentian Yiolet for Methyl Violet, as the former stains more 

 quickly and does not wash out so readily in Alcohol. 



Koch produces an isolated staining of bacteria in sections, 

 by staining them in aqueous solution of Methyl Violet, 

 Fuchsine, or Methylene Blue, and washing them in a saturated 

 aqueous solution of Carbonate of Potassium diluted with an 

 equal bulk of water ; this removes the colour from the nuclei, 

 leaving the bacteria stained : the sections are then dehy- 

 drated, cleared and mounted. 



The general methods now adopted are : 



