132 SUMMARY OF CURRENT RESEARCHES RELATING TO 



is placed on the slide, and made to spread over the surface by turning 

 the slide about — not by using the needle. Excess is removed with 

 blotting-paper, and the films are allowed to dry at room temperature. 

 The film is not fixed. The stain is made by dissolving 1 grm. of tannic 

 acid, 1 grm. of potash-alum in 40 ccm. distilled water, and adding 

 0*5 grm. of night-blue dissolved in 20 ccm. of absolute alcohol. The 

 precipitate is removed by filtration, and the filtrate is the stain. The 

 slides are stained for 2 minutes and then washed in running water. 

 Only the flagella are stained, and in order to show up the body of the 

 cell a contrast stain is used. Anilin-water-gentian-violet gives a good 

 contrast. 



As the night-blue staining is caused by precipitation, it is advised 

 to filter the solution on to the slide ; or the preparation may be over- 

 stained and decolorised in dilute alcohol. The results obtained by this 

 process are better and more certain than those of any other method yet 

 described. 



Mr. A. Moore * states that night-blue is very effective for staining 

 capsules, e.g. Diplococcus pneumonise, Pneumobacillus, and M. tetragenus. 

 A thin film of liquid serum culture is spread on a slide, dried, fixed 

 with dilute acetic acid, and washed with distilled water. The pre- 

 paration is then stained with carbcl-fuchsin for about a minute, washed 

 again, and dried. The night-blue stain is then applied for one or two 

 mimites, aided if necessary by gentle heat, then washed and dried. 



New Method of Flagella Staining.! — Dr. E. Welcke adopts the 

 following procedure for staining flagella. The agar culture should ba 

 less than 24 hours old ; the bacteria should be killed with 4 per cent, 

 formalin or 1 per cent, osmic acid solution. The film is fixed by heat, 

 and when cold mordanted with Loeffler's or Bunge's fluid, diluted to 

 from 1 to 4 or 1 to 20. After washing and removing the water, the 

 preparation is treated with silver oxide-ammonia solution and heated 

 until it begins to brown. After having been washed, it is immersed in 

 1 per cent. HgCl 2 solution for 1/4 minute. It is again washed, and the 

 treatment with silver-oxide-ammonia solution repeated for 1, 2, or '6 

 minutes. It is washed again and treated with rodinal- or menthol- 

 developer for 1/4 minute. It is then washed and dried. 



Demonstrating the Structure of Bacteria.^: —Mr. S. Eowland, for 

 his observations on the structure of bacteria, selected rosein, as this stain 

 is extremely soluble, innocuous to the organisms examined, and possesses 

 a distinctive and constant differential staining power for certain parts 

 of the bacterial cell. A drop of the culture is placed on a slide and 

 surrounded with droplets of stain, and then mixed together with a needle. 

 A cover-glass is then superposed. With a little practice the amount 

 of fluid between the glasses was so graduated that, while movement was 

 prevented, crushing was avoided. Plasmolysis did not occur if the 

 precautions were properly adhered to. 



In order, as far as possible, to avoid errors of interpretation, the violet 



* Tom. cit., p. 244. 



t Arch. f. Klin. Chirurgie, lix. (1899) pp. 129-40 (4 figs.). 



X Trans. Jenner (late British) Inst. Prev. Med., ser. ii. (1899) pp. 143-60 (1 pi.) 



