192 BACTERIOLOGY. 



of water, and from this they are again tlioroughly 

 washed in water, then in absolute alcohol containing 

 enough methylene-blue in substance to give it a toler- 

 ably dense color, then for a few minutes in aniline oil 

 to which a little methylene-blue in substance has been 

 added, then completely rinsed out in pure aniline oil ; 

 from this they are passed into thymol or oil of turpen- 

 tine for two minutes, and then into xylol, from which 

 they are mounted in xylol-balsam. The advantages 

 of this method are that it is generally applicable, and 

 by its use the bacteria are not robbed of their color, 

 whereas the tissues are sufficiently decolorized to render 

 the bacteria visible and admit of the use of contrast- 

 stains. 



Weigert's modifioation of Gram's method for sections. 

 Stain the sections in the Koch-Ehrlich aniline-water 

 gentian-violet solution for five or six minutes ; wash 

 in water or physiological salt-solution (0.6 to 0.7 per 

 cent, solution of sodium chloride in distilled water) ; 

 transfer them with the section-lifter to the slide ; take 

 up the excess of fluid by gently pressing upon the flat 

 section with blotting-paper ; treat the section with the 

 iodine solution used by Gram ; take up the excess of 

 the solution with blotting-paper ; cover the section ^vitli 

 aniline oil — this not only differentiates the component 

 parts of the section, but dehydrates as well ; wash out 

 the aniline oil with xylol, and mount in the usual way 

 in xylol-balsam. Or, decolorization with iodine may 

 be omitted, and the sections, after staining in the ani- 

 line-water gentian-violet for five or six minutes — or 

 longei", if necessary — are transferred to the slide without 

 being washed in water or ' salt-solution (or, if so, only 

 very slightly and rapidly), dried as completely as possi- 



