STAINING OF FLAGELLA 71 



on the cover-glass or in watch glasses while the process is 

 going on. "When, however, sections of tissue containing 

 bacteria are to be warmed, precautions must be taken to 

 avoid spoiling the tissue, especially as staining takes 

 longer in the case of sections. 



Staining of flagella.— For the purpose of rendering 

 visible the flagella of motile micro-organisms, Loffler uses 

 a mixture of 10 c.cm. of a 20 per cent, solution of tannin 

 and a few drops of saturated ferrous sulphate solution, 

 with fuchsine or 4 or 5 c.cm. of extract of logwood. Stain- 

 ing is effected with fuchsine in aniline water, to which a 1 

 per 1,000 solution of caustic potash has been added until it 

 becomes turbid owing to a floating precipitate. For bacteria 

 which form alkalies, the mordant must be rendered corre- 

 spondingly acid ; for those which form acids, alkaline. 



According to Trenkmann the cilia are brought into view 

 if the preparations are treated before staining with tannin 

 and hydrochloric acid or catechu tannic acid to which 

 carbohc acid has been added, or extract of logwood treated 

 with acid ; and they become still more distinct if the pre- 

 parations, after being treated with the mordant and stained, 

 are examined in a drop of iodine water. Two or three 

 drops of boiled water are allowed to fall upon a slide, and a 

 small drop of the culture to be examined is added and 

 mixed well in. A minute droplet is conveyed from this to 

 a cover-glass, spread out, dried in air, and laid without 

 previous heating in a solution containing 2 per cent, of 

 tannin and ^ per cent, of hydrochloric acid. The cover- 

 glass remains for from 6 to 12 hours in this solution, and 

 is then washed in water, laid for an hour in iodine water, 

 washed again, and deposited for half an hour in a weak 

 solution of gentian violet in aniline water. 



Staining of spores. — It is possible to effect a staining of 

 the spores, in those micro-organisms which form them, by 



