Sessional_Paper_1907 — Page 875

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These notes are merely a summary of the positive results obtained up to date. No attempt has been made to give full descriptions of the parasites and their behaviour during development as up to the present it has been impossible to obtain accurate photographic pictures of them.

A considerable amount of time has been devoted to the study of the cycles of develop- ment of Halteridium and the relationship of the different parasites of the frog to each other.

Further the majority of Trypanosomata found have never been accurately described. It is hoped that, in the near future, we shall be able to furnish fuller and accurate data as to many of these hæmatozoa, the life history of which can be studied only in the tropics.

The Bacteriological Examination of the Public Water Supplies.

These examinations were commenced in the month of August. Samples are now collected monthly from the Pokfulam and Tytam supplies, from the Kowloon service, and the Cheung Sha Wan supply.

The methods, which have been adopted in all of these systematic examinatious, were directed chiefly to the number of micro-organisms per c.c. of the sample, the presence of any organisms of contamination, and the presence of any specific organisms of disease.

These periodic bacteriological examinations are of considerable value in regard to the efficient filtration of water supplies. In this connection the number of bacteria per c.c. returned in bacteriological reports is of great comparable value in forming an opinion as to pollution or as to failure of filtration. Further the cumulative experience of bacteriologists strongly supports the one criterion of efficiency of filtration, viz., the absence in the filtered water of putrefactive and disease producing micro-organisms, which can only be ascertained by regular bacteriological examinations.

The general results of the examinations of the public water supplies of Hongkong show the water to be of great bacteriological purity. This is especially so in regard to the supply from Pokfulam and Tytam reservoirs. The number of micro-organisms present in the samples has generally remained below 100 per c.c., and the filtered water supplied to Victoria contains fewer bacteria than the metropolitan water supply in London. At no time, since these examinations were commenced, has it been possible to find the slightest trace of sewage or other form of organic contamination.

The Bacteriological Examination of Water from Other Sources.

(1.) Well Water.

Several samples have been examined. In each case the water showed evidence of organic pollution, and the presence of micro-organisms indicating recent sewage con- tamination.

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(2.) Nullah Water Supply.

All the samples examined showed the presence of sewage, and were unfit for potable purposes.

(3.) Water from dwellings in which cases of Typhoid Fever had occurred. In all the samples examined the water was good for potable purposes.

The Significance of "Bacteria of Indication” of Contamination in Water. The chief bacterium of indication of contamination is B. coli. A considerable difference of opinion exists as to the exact significance of its presence in a sample of water.

The mere presence of B. coli, by itself, in a water is not of importance, because the organism, under ordinary conditions, is likely to be harmful, but rather because it serves as an index of sewage or surface pollution. B. coli is an organism closely related to sewage, and is of importance owing to its potential pathogenicity and similarity to the typhoid bacillus.