NEW METHODS OF USING THE ANILINE DYES. 407 



the exit of the dye from the bacteria can be eflPectually pre- 

 vented. 



When cleared the sections are removed from the benzine 

 clove-oil mixture to oil of cloves containing eosin. The eosin 

 stains the background red and at the same time turns out the 

 excess of Spiller^s purple; sometimes a few seconds, sometimes 

 a few minutes, are required to do this. The sections are then 

 washed in oil of cloves, passed through the benzine and clove- 

 oil mixture to benzine and mounted. 



The removal of the excess of colour can be greatly hastened 

 by moving the sections backwards and forwards between the 

 oil of cloves and benzine and clove-oil mixture.^ 



I attempted also to stain in this manner with fuchsin and 

 gentian violet, but found that although the sections were left 

 in the dyeing solution only for a few seconds they were hope- 

 lessly overstained, and it was impossible to remove the excess 

 of colour by means of oil of cloves. 



After some trouble I succeeded in finding out how to avoid 

 this difficulty. The method is as follows: 



The sections are subjected to double treatment with fuchsin 

 or gentian violet in the same way as above described for Spil- 

 ler's purple, then rapidly dehydrated in alcohol and placed 

 in the benzine and clove-oil mixture. They are then removed 

 to oil of cloves in which picric acid has been dissolved. This 

 quickly turns out the excess of fuchsin or gentian violet and at 

 the same time stains the background. The sections are then 

 washed in pure oil of cloves, benzine and clove-oil mixture, 

 placed in benzine and mounted. Or if a green background is 

 preferred to the yellow tint of picric acid the sections may be 

 contrast stained with a mixture of methyl blue snd picric acid 

 dissolved in oil of cloves or aniline. They must then be washed 

 rapidly in benzine clove-oil mixture and placed in benzine. 



The only objection to the use of gentian violet by this method 



^ This is really the reiteration of a "tip" kindly shown me by Mr. Liugard 

 at the Brown Institution. He showed lue that in staining by Gram's method 

 it is possible to turn out the excess of colour by moving the sections from 

 alcohol to oil of cloves, and back again repeatedly. 



