. Bacteria, especially as they are related to the economy of nature. Bacteriology. 52 BACTERIA 2000 or 3000 cc. of the suspected water through a Berkefeld filter. When this has been accomplished, by means of a sterile brush the particulate matter on the candle of the filter is brushed off into 10 or 15 cc. of sterilised water. This simple ar- rangement is analogous to the use of gravity or centrifugal methods of securing the solid matter in milk. The smaller quantity of water is then readily examined, and scanty germs more readily detected. A second point elaborating the scheme of water exam-
. Bacteria, especially as they are related to the economy of nature. Bacteriology. 52 BACTERIA 2000 or 3000 cc. of the suspected water through a Berkefeld filter. When this has been accomplished, by means of a sterile brush the particulate matter on the candle of the filter is brushed off into 10 or 15 cc. of sterilised water. This simple ar- rangement is analogous to the use of gravity or centrifugal methods of securing the solid matter in milk. The smaller quantity of water is then readily examined, and scanty germs more readily detected. A second point elaborating the scheme of water exam- ination is the choice of media for sub-cultur- ing. Mere examination on gelatine is not sufificient. Even in making the primary "1 plate cultivations it is well to vary the media —agar, carbol-gelatine, Eisner, etc. But when colonies have appeared upon these plates it is important to sub-culture with accuracy and good judgment upon all or any media—gelatine, agar, broth, potato, milk, blood serum, glucose agar, glycerine agar, etc.—that will reveal the real characters of the bacteria present. A method proposed by Professor Sheridan Delepine is to place some of the suspected water in sterilised test-tubes without further treatment, and incubate at ij"" C. for twelve or eighteen hours, and then plate out and estimate the number of bacteria as in the ordinary course. " In polluted water, containing an excess of organic matter," he says, " an extremely rapid multiplication of bacteria is observed. In unpolluted water, containing only water bacteria and a very small amount of organic matter, very little or no multiplication takes place, and the growth of the water bac- teria liquefying gelatine is checked to a remarkable ; Thirdly, by none of these methods should we be able to. Berkekelu Filter In Position for Filtra- tion of Water to be Please note that these images are extracted from scanned page images that may have been
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