The principles of bacteriology : a practical manual for students and physicians / by A.C. Abbott.

Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: The principles of bacteriology : a practical manual for students and physicians / by A.C. Abbott. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    the cotton into the tube, and their spores have fallen upon the surface of the serum and gone on to develop. Special Media.—The media just described—bou- illon, nutrient gelatin, nutrient agar-agar, potato, and blood-serum—are those in general use in the laboratory for purposes of isolation and study of the ordinary forms of bacteria. For tbe finer points of differentiation special media have been suggested; a few of them will be mentioned. 3£i(k Fresh milk should be allowed to stand over night in the icerchest, the cream then removed, and the remainder of the milk pipetted into test-tubes, about 8 c.c. to each tube, and sterilized by the intermittent process, at the temperature of steam, for three successive days. The cream is best separated from the milk by the use of a cylindrical vessel with stop-cock at the bottom, by means of which the milk, devoid of cream, may be drawn off. A Chevallier creamometer with stop-cock at the bottom serves the purpose very well. It should be covered while standing. Milk may be used as a culture medium without any addition to it, or, before sterilizing, a few drops of litmus tin(!ture may be added, just enough to give it a pale blue color. By this means it may be seen that dif- ferent organisms bring about different reactions m the medium; some prodmnng alkalies which cause the blue color to be intensified, others producing acids which change it to red, while otliers bring about neither of these changes. Milk may also be employed as a solid culture medium by the addition to it of gelatin or agar-agar in the pro- portions given for the preparation ot the ordinary nutri-