Sessional_Paper_1911 — Page 191

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As regards standards for B. Coli used at Home that suggested by Houston (1902-3) as a tentative standard is probably the most generally accepted. It is stated to be clearly meant to be governed or controlled by knowledge of local conditions and other circumstances.

Class 1.

100 c.c.

A water showing no evidence (bacteriologically) of recent objectionable contamina- tion, and therefore, in the absence of conditions of an actually or potentially dangerous kind, seemingly "safe" for domestic use.

―

Class 2. + 100 c.c., 10 c.c.

A water showing appreciable evidence (bacteriologically) of presumably objectionable contamination, and therefore not absolutely free from the suggestion of being potentially, if to an almost negligible extent, dangerous to health.

Class 3. + 10 c.c.,

- 1 c.c.

A water showing definite evidence (bacteriologically) of contamination presumably objectionable in character, and therefore to be regarded with some suspicion.

Class 4. + 1 c.c.,

-

•1 c.c.

A water showing such obvious indications (bacteriologically) of pollution, presumably objectionable in character, as hardly to fall within the category of waters reasonably safe for potable purposes in the absence of contra-indications of a convincing kind.

Class 5+1 cc.,

-

'01 c.c. A water showing such clear evidence (bacteriologically) of presumably objectionable contamination as to be quite unfit for domestic use, on the basis of this test.

Class 6.01 c.c., ·001 c.c. A good sewage effluent.

Further comment is superfluous.

The question of what standards can be applied in the Tropics will be better con- sidered after the results of the samples have been examined.

THE PRESENCE OF PATHOGENIC ORGANISMS

such as Bacillus Typhosus and the Cholera Vibrio in water.

Some remarks are necessary to explain the absence of any investigation into the water for pathogenic organisms. The statement is frequently made in Reports on water that "no pathogenic organisms are present". This conveys rather a misleading idea as from it, it might be thought that the isolation of these organisms, if present, is an easy and certain

matter.

It would be well perhaps to briefly notice what is the probability of isolating these organisms from a water.

Willson (1905) in his paper on the isolation of B. Typhosus from water could only find six genuine cases in which B. Typhosus has ever really been isolated from water- supplies in the past. Of these six cases, four were wells in which the contamination would be much more direct than it would be in a large catchment area; the two remaining cases were the Berlin Water Works in 1895 and the Prague Water Supply in 1904.

Houston (1910) during 1907 and 1908 examined 156 samples of sewage polluted river water using tried methods. Out of 7,329 selected microbes from these samples not one could be identified as B. Typhosus.

It is of course quite an easy matter, as Houston points out, to isolate Typhoid-like organisms and this accounts probably for the numerous reported cases of isolation of True Typhoid Bacilli.

Quite recently Volpine and Cler (1911) have recommended the use of the complement fixation method for the detection of Typhoid Bacilli in drinking water but not enough work has yet been done to prove its practical value.

Unless some improved method is devised it is obviously of no value to say these organisms are not present or could not be found without carrying out a very large amount of work.

As regards Cholera, there does not appear to be any reasonable chance of the Water Supply becoming infected. Cholera is not endemic in Hongkong and the few imported cases which occur should not have any opportunity of contaminating the Supply.