OF THE HUAIAH SUBJECT. 51 



bacillus) this method does not satisfactorily clear the prepara- 

 tion, i.e., decolorize the ground substance in which the bacteria 

 lie. 



Under such circumstances, the cover-glasses, after being 

 prepared with the bacteria and allowed to dry, are to be left for 

 ten minutes in a capsule or saucer of 20 per cent, solution of 

 acetic acid ; after which they are washed in distilled water, al- 

 lowed to drain and to dry, edgewise, on filter-paper, and after- 

 wards stained in the usual manner, the subsequent washings 

 being carried out without acetic acid. It is not requisite to pass 

 the films across the flame at any stage of the procedure, even if 

 the cover-glasses have been prepared from broth cultures. Even 

 this at times fails to give clean preparations (as, e.g., in the case of 

 the glanders bacillus) ; the use of saturated alcoholic solution of 

 gentian violet, left on the cover- glass for an hour (beneath a 

 watch glass), will often then give satisfactory results ; the wash- 

 ing in such circumstances should be carried out rapidly in water 

 to which no acetic acid has been added. 



