An inquiry into the relative efficiency of water filters in the prevention of infective disease / by G. Sims Woodhead and G.E. Cartwright Wood.

  • Woodhead, German Sims, Sir, 1855-1921.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: An inquiry into the relative efficiency of water filters in the prevention of infective disease / by G. Sims Woodhead and G.E. Cartwright Wood. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    143/152 (page 131)
    filtering medium, when this is inefficient, present in a filter in all probability affects merely the period over which the disease germs would continue to be distributed in the filtrate, as the greater proportion of these will ultimately be washed through more or less rapidly, according to the depth of the medium which they have to traverse. An ineflacient filter which received on one occasion water charged with disease germs would probably merely distribute these disease germs in the filtrate for a greater or less period of time, instead of the consumer receiving the disease germs all at one time where filtration was dispensed with. We have already sug- gested that in our opinion the effect of such a filter would be to materially increase the risk of infection without decreasing the severity of the disease, since the chances of the micro- organism passing unharmed into the small intestine and finding there suitable conditions would be greatly increased by its distribution over a more prolonged period. Water an Unsuitable Medium for Disease Germs. We are, however, unable to support the view that eithei cholera or typhoid fever germs can find a suitable breeding ground in any of the ordinary filtering media, and that from this cause the filter may continue to infect the water supplied. We have been unable to find any evidence that either of these organisms can multiply in water, even when highly polluted with sewage, and are accordingly strongly of opinion that the presence of disease germs in the filtrate from an infected filter is not to be ascribed to their multiplication, but to the germs originally introduced being gradually washed through into the receiver. We regard the experiments with perfect filters fed with raw sewage, where disease germs were unable to grow through into the filtrate, as strongly supporting this view. The history of epidemics spread by means of drinking water are also against the assumption that the germs multiply in this medium, since it has been observed that where a supply has been accidentally con- taminated, but where the contamination has afterwards been cut off, the epidemic which originates through the drinking water does not continue to spread as one might legitimately expect if the germs were undergoing multiplication. It may be suggested, however, that the organic matter which has been retained in the pores of the filter may aflord them sufli- cient nutritive pabulum; but the experiments which we have described with filters which had been in prolonged use, steri- lised and unsterilised, give no support to this hypothesis. We do not indeed deny that these germs can multiply out- side the living body; indeed, we believe that both are cap- able, under favourable conditions, of undergoing a sapro- phytic stage, but we believe that the necessary conditions are