An introduction to practical bacteriology for physicians, chemists, and students / by W. Migula ; translated by M. Campbell and edited by H. J. Campbell.

  • Migula, W. (Walter), 1863-1938.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: An introduction to practical bacteriology for physicians, chemists, and students / by W. Migula ; translated by M. Campbell and edited by H. J. Campbell. Source: Wellcome Collection.

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    thing wliich is still more injurious. The sulphuric acid adds very much to the staining power of the raethy- lene blue, and lience the partially, or entirely, de- colourised tubercle bacilli may become coloured violet or light blue. Thus if there should be only a few present, and if these olfered only a comparatively slight resistance to the decolourisation, they might possibly be, by this method, completely overlooked, as they would appear against the darker blue back- ground only as light blue rods which might just as well belong to any other slender species of bacillus. Similarly there are great objections to the method of allowing the layer of sputum to dry on a slide, and of fixing and staining it there. Much more heat must, of course, be employed in Order to fix a slide prepara- tion than is necessary if a thin cover-glass be used; and as in addition the slide retains the heat much longer, there is too much of a good thing. The bacilli become overheated, and in consequence lose partially, or entirely, tlieir power of absorbing the stain, and bence it is impossible to obtain really good prepara- tions by this means. In the place of the 5 per cent. solution of sulphuric acid, a 3 per cent. solution of hydrochloric acid in absolute alcohol may be used. A 20 per cent. solu- tion of nitric acid has a wonderfully quick effect; some- times a more dilute solution answers the purpose. Nitric acid, however, must always be used with great