THE STAINING OF BACTERIA 95 



Crystal violet. 



Blue Stains. Methylene-blue 1 (synonym : phenylene-blue). 

 Victoria- blue. 

 Thionin-blue. 



Red Stains. -Basic fuchsin (synonyms : basic rubin, magenta). 

 Safranin (synonyms : fuchsia, Girofle). 



Brown Stain. Bismarck- brown (synonyms: vesuvin, phenylene- 

 brown). 



It is of the greatest importance that the stains used by the 

 bacteriologist should be good, and therefore it is advisable to 

 obtain those prepared by Griibler of Leipzig. One is then 

 perfectly sure that one has got the right stain. 



Of the stains specified, the violets and reds are the most 

 intense in action, especially the former. It is thus easy in using 

 them to overstain a specimen. Of the blues, methylene-blue 

 probably gives the best differentiation of structure, and it is 

 difficult to overstain with it. Thionin-blue also gives good 

 differentiation and does not readily overstain. Its tone is deeper 

 than that of methylene-blue and it approaches the violets in tint. 

 Bismarck- brown is a weak stain, but is useful for some purposes. 

 Formerly it was much used in photomicrographic work, as it 

 was less actinic than the other stains. It is not, however, 

 needed now, on account of the improved sensitiveness of plates. 



It is most convenient to keep saturated alcoholic solutions 

 of the stains made up, and for use to filter a little into about 

 ten times its bulk of distilled water in a watch-glass. A solution 

 of good body is thus obtained. Most bacteria (except those of 

 tubercle, leprosy, and a few others) will stain in a short time in 

 such a fluid. Watery solutions may also be made up, e.g. a 

 saturated watery solution of methylene-blue or a 1 per cent 

 solution of gentian- violet. Stains must always be filtered before 

 use ; otherwise there may be deposited on the preparation 

 granules which it is impossible to wash off. The violet stains in 

 solution in water have a great tendency to decompose. Only 

 small quantities should therefore be prepared at a time. 



The Staining of Cover-glass Films. Films are made from 

 cultures as described above. The cover-glass may be floated on 

 the surface of the stain in a watch-glass, or the cover-glass held in 

 forceps with film side uppermost may have as much stain poured 

 on it as it will hold. When the preparation has been exposed for 

 the requisite time, usually a few minutes, it is well washed in 

 tap water in a bowl, or with distilled water with such a simple 

 contrivance as that figured (Fig. 44). The figure explains itself. 



1 Tliis is to be distinguished from methyl-blue, which is a different com- 

 pound. 



