THE USE OF STRONGER STAINING SOLUTIONS, in 



those whieh are least stained^ as material for oar pare 

 cultures. 



Various substanceSj mostly alkaline, may be added 

 to the staining solutions, in order to render them 

 sufficiently powerful to stain these bacteria. The 

 most important of these substances is Aniline, which 

 is a peculiar, light yellow, oily flaid. The solutions 

 may be prepared in several ways, the simplest and 

 most satisfactory being the following : — 100 ccm. of 

 distilled water is thoroughly well shaken up with as 

 much aniline as it can dissolve (about 4 ccm.) ; it is 

 then filtered through a good filter to remove all the 

 unabsorbed aniline, and 5 grm. of solid fuchsine 

 (rubine) are added to it. The greater part of the 

 fuchsine becomes dissolved if it is allowed to remain 

 for twenty-four hours in the mixture, which should 

 be repeatedly shaken. The staining solution is then 

 ready for use. 



In order to stain a fixed dry cover-glass preparation 

 with this solution, it is best to pour a few drops of it 

 through a filter straight on to the cover-glass. If the 

 solution is not filtered, oily stain precipitates are apt 

 to be deposited upon the cover-glass, and as these are 

 only removed with great difficulty, they very fre- 

 quently spoil the preparation. The solution may be 

 kept for from four to six weeks; it then commences to 

 decompose. It is best to keep it in the dark in a 

 bottle, which is made air-tight by means of an india- 



