The bacteriological examination of food and water / by William G. Savage.

  • Savage, William George, Sir, 1872-
Date:
1914
Catalogue details

Licence: In copyright

Credit: The bacteriological examination of food and water / by William G. Savage. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    methods, often a procedure of no great trouble or complexity. On the other hand their isolation from water, food, air, etc. is frequently a matter of the utmost difficulty for reasons which readily present themselves. In these substances any pathogenic bacteria are frequently present in but small numbers compared with the total number of bacteria present, while these competing bacilli, by growing more readily and abundantly in the media used for the isolation of the pathogenic bacteria, may materially enhance the difficulties of isolation. Further, there is always the possibility that any pathogenic bacteria originally present may have been completely eliminated by the time attention is called to the need for bacteriological examination. These pathogenic bacteria in water, soil or even in milk are, or may be, in an environment either in itself unsuitable to their multiplication and sustained life or in one relatively unsuitable compared to that enjoyed by the horde of naturally present, or added, competing bacilli. This may cause their actual or relative disappearance when the food or water is submitted to bacterio- logical examination. For these reasons the isolation of specific pathogenic bacteria plays but a small part in this class of bacteriological analysis. The second object of a bacteriological examination—to measure undesirable bacterial contamination—is by far the most valuable part of the bacteriological examination of the materials under consideration. By modern methods it is possible not only to say whether such pollution exists but, with considerable approach to accuracy, to determine the extent of such pollution and to furnish data as to the degree of its harmfulness. Although the substances to be examined are various while the sources of pollution are many and not all of the same character there is for most of them a broad relationship as to the nature of the pollution to be detected and measured. For example, for water supplies bacteriological analysis is mainly concerned with the detection and estimation of excretal and sewage pollution. For shellfish the degree of sewage pollution is again the object of the examination. For milk, apart from the detection of pathogenic bacteria, the examination is chiefly