THE STAINING OF BACTERIA. 53 



for one-quarter minute in absolute alcohol. After this it is 

 transferred to xylol for one-half minute, then lifted to a slide, 

 mounted in Canada balsam, and examined. 



3. Weigert's Modification of Gram's Method. 



Stain sections in the Koch-Ehrlich anilin-water gentian-violet 

 solution for five or ten minutes ; wash them afterward in 

 water or physiological salt solution. Transfer to slide and 

 remove excess of fluid with blotting-paper. Treat with the 

 iodine solution of Gram for three minutes. Take up the ex- 

 cess of solution with blotting-paper. Cover the section with 

 anilin oil, wash out the oil with xylol, and mount in xylol 

 balsam. The anilin oil in this case acts as a decolorizing 

 agent, and should be removed carefully, otherwise the speci- 

 men will not keep. 



4. Kuehne's Carbolic Methylene-Blue Method. 



Put the sections into the following solution for one-half 

 hour : 



Methylene-blue in substance, 1^ part ; 



Absolute alcohol, 10 parts. 



Rub thoroughly in a mortar, and when the blue is completely 

 dissolved add 100 parts of a 5 per cent, carbolic acid solu- 

 tion. This solution should be made fresh when needed. 

 The sections are stained for fifteen minutes in this solution 

 and then washed in water until free from it. They are 

 next transferred to a 2 per cent, hydrochloric acid solution, 

 then to a solution of carbonate of lithium (of the strength of 

 6 to 8 drops of a concentrated watery solution of the salt 

 to 10 drops of water), and from this they are again washed 

 in water and in absolute alcohol containing sufficient meth- 

 ylene-blue in substance to give it a blue color, then for a few 

 minutes in anilin oil to which a little methylene-blue in sub- 

 stance has been added, and they are then rinsed out in pure 

 anilin oil ; from this they are placed in oil of turpentine or 

 thymol for two minutes, then in xylol, and mounted in xylol 

 balsam. 



