But whatever merits they had as clarifiers of turbid water, the advent of bacteriology, and the recognition of the fact that the bacteria of certain diseases may be water-borne, introduced a new criterion of effectiveness, and it was perceived that the removal of solid particles, or even of organic impurities (which were realized to be important not so much because they are dangerous to health per se as because their presence affords grounds for suspecting that the water in which they occur has been exposed to circumstances permitting contamination with infective disease), was not sufficient; the filter must also prevent the passage of pathogenic organisms, and so render the water sterile bacteriologically.
It was certainly present in August, but was not recognized until the 23rd of September, and the diagnosis was not bacteriologically confirmed until the 13th of October.
Plague was suspected, but Dr Muller, who attended the man and had studied the disease in India, would not admit the diagnosis on clinical grounds, nor was it bacteriologically established until the 19th of October.