Agricultural bacteriology : theoretical and practical / by John Percival.

  • John Percival
Date:
1910
Catalogue details

Licence: In copyright

Credit: Agricultural bacteriology : theoretical and practical / by John Percival. Source: Wellcome Collection.

    27/434 page 9
    (a) Saturated alcoholic solution of gentian violet, 30 c.c. Aniline water, 100 c.c. As this solution does not keep well, only a small amount should be made up. The aniline water is obtained by thoroughly shaking up 4 c.c. of aniline with 100 c.c. of water, and then filtering through moist filter paper until the liquid is clear and free from any oily drops ; any aniline which remains in the bottom of the flask or tube after shaking should not be poured on the filter. (b) Iodine 1 gr. Potassium iodide . . . . 2 gr. Water ...... 300 c.c. Dissolve the potassium iodide in about 10 c.c. of the water and add the iodine : when the latter is dissolved add the rest of the water. In using the above solutions for staining purposes, the follow- ing procedure should be adopted :— (1) Float the cover-glass, film downwards, on aniline-gentian- violet solution in a watch-glass, and allow the stain to act for five minutes. Take up with forceps and drain off the superfluous stain by dipping the edge of the cover-glass on blotting-paper. (2) Then, immerse the cover-glass for 1-2 minutes in the iodine solution in a watch-glass, film side up. The purple colour of the gentian violet should change to a yellowish brown tint. (3) Now, remove the cover-glass, taking care to note on which side the bacteria are ; drain off the superfluous liquid and dip the cover-glass into a vessel containing absolute alcohol for 10 seconds, and into a second vessel of absolute alcohol for 10-15 seconds ; when no more of the gentian violet stain is seen to wash off, take it out and wash it in water, and examine either in water or after drying in Canada balsam. Too long immersion in alcohol must be avoided.
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