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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    useful specific characteristic, by means of whicb these species can be disfcinguished from others, in whicb such streaks never occur, except in quite old culti- vations. It niay be further observed that soine species stain easily and intensely; whilst others of the same age only become coloured very slowly, and even if they are left for a long time in the staining solution, never be- oome intensely red or violet. This is partly cansed by the fact that some kinds grow old earlier than others, and hence with these mach younger cultures than usual must be used; and partly that some bacteria absorb staining reagents much more readily than others. There are bacteria which only become imper- fectly coloured even when they remain for days in the staining solution. These diflferences in their behaviour towards staining reagents are of great use in diflferen- tiating various species. Great variety is also shown in the persistency with which different kinds retain their colour when once stained. If we make such stained cover-glass preparations of a number of species with material obtained frora our pure cultures, we shall very soon notice how differ- ently various species behave towards decolourising reagents. First, let us try the efiect of a very weak decolouriser, ten per cent. alcohol. In half a minute it is seen that nearly all the species have parted with a large proportion of the staining material that they had