Mr. F. A. Dallyn, who was one of the six consulting engineers to advise the commission, presented a minority report, in which he eliminated Paragraphs 5, 7, and 11, and made a few slight changes in some of the other paragraphs.

BACTERIOLOGICAL STANDARD FOR DRINKING WATER ADOPTED BY THE
TREASURY DEPARTMENT FOR WATER SUPPLIED TO THE PUBLIC
BY COMMON CARRIERS IN INTERSTATE COMMERCE.

On October 21, 1914, the Treasury Department adopted the standard for interstate carriers for water supplies for public drinking purposes in accordance with the recommendations by a commission appointed by the Secretary of the Treasury, January 22, 1913. This commission of fifteen sanitarians recommended a standard published in the United States Public Health Reports, vol. 29, No. 45, p. 2960, dated November 6, 1914, as follows:

"I. The total number of bacteria developing on standard agar plates incubated twenty-four hours at 37° Centigrade shall not exceed 100 per cubic centimetre: Provided that the estimate shall be made from not less than two plates, showing such numbers and distribution of colonies as to indicate that the estimate is reliable and accurate.

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2. Not more than one out of five 10 cubic centimetre portions of any sample examined shall show the presence of organisms of the bacillus coli group when tested as follows:

"(a) Five 10 cubic centimetre portions of each sample tested shall be planted, each in a fermentation tube containing not less than 30 cubic centimetres of lactose peptone broth. These shall be incubated fortyeight hours at 37° Centigrade and observed to note their formation.

"(b) From each tube showing that more than five per cent. of the coli are in the fermentation tube, plates shall be made after forty-eight hours' incubation upon liquid lactose litmus agar or endo media.

"(c) When plate colonies resembling B. coli develop upon either of these plate media within twentyfour hours, a well-isolated characteristic colony shall

be fished and transplanted into a lactose broth fermentation tube which shall be incubated at 37° Centigrade for forty-eight hours.

"Examining this above recommended standard, it will be noted that, roughly proportioning, twenty per cent. of the 10 cubic centimetre samples will be permitted to give positive indications of B. coli. These tests, however, are not to secure presumptive tests of the lactose peptone bile gas formation method; they are something nearer to the typical coli test. Accordingly the number of samples showing B. coli by presumptive tests may well run to forty per cent. of the 10 cubic centimetre samples. Comparing this forty per cent. standard, we note that the New York drinking water, as supplied in the 135th Street gate-house, showed a yearly average, in 1912, of forty-four per cent. positive results in 10 cubic centimetre samples, and in 1911 an average of seventy-six per cent. positive results.

Assuming that water with forty per cent. positive results corresponds with the recommendations of the committee, the efficiency of the filtration and sterilization system, when compared with the permissible limits in raw water for filtration purposes as recommended by the International Joint Commission's sanitary experts, ought to correspond roughly to ninety-nine per cent."

The Treasury Commission state further as quoted herein: "The bacteria developing on standard gelatine at 20° Centigrade include a relatively large proportion of harmless bacteria, which are normally inhabitants of falls and natural waters, free from dangerous pollution. The number of bacteria as estimated by the standard gelatine count serves in a general way as an index of the cleanliness of the sample; but to properly interpret the result of such a count it is necessary to have knowledge of the source of the sample examined and the nature of the pollution to which it has been exposed and the opportunity afforded for multiplica

tion of the harmless varieties of bacteria present; on account of rapid multiplication of harmless varieties of bacteria which may take place when water is stored in small containers at moderate temperatures, and the impossibility of making approximately correct allowance for such multiplication, it is believed that the attempt to establish a limit to bacteria developing on gelatine is not practicable for the purposes of the control of supplies of common carriers.

"The bacteria developing on standard agar at 37° Centigrade in twenty-four hours are also chiefly varieties which are entirely harmless. The agar count, however, as compared with the gelatine count, represents a larger proportion of bacteria which find their normal habitat in the animal body and are present in sewage and other discharges from the animal body. Generally speaking, an accepted agar count is sufficient to cause at least a suspicion that the water is polluted with discharges from animal bodies, and is therefore unsafe for use as a drinking water. Multiplication of the harmless varieties present may, however, take place at ordinary temperatures in water stored in tanks, coolers, bottles, and other containers, thus greatly increasing the agar count without, of course, increasing the actual dangerous pollution of the water. This introduces a large source of error into the attempt to interpret the significance of agar count of samples of water stored for varying lengths of time under conditions more or less favorable to bacteria multiplication. It is largely for this reason that it has been considered necessary to allow varying limits to the agar count of the water supplies of common carriers, and to attach to the result of this method of examination a significance much less than ordinarily attaches to the agar count in examining samples of water especially removed from known

sources.

"Bacteria of the bacillus coli group are normally inhabitants of the intestinal tract of warm-blooded animals, and it is believed that under ordinary conditions they do not multiply in nature outside of the animal.

body; that in drinking water supplies they tend, on the
contrary, to die out rather rapidly. The presence of
such bacteria in the water may accordingly be con-
sidered valid evidence that the water has been polluted
with the intestinal discharges of some of the higher
animals, and the numbers present should be considered
a fair index of the extent of such pollution. Since
practically all of the diseases which are known to be
commonly transmitted through water supplies are due
to germs which are discharged from the intestines of
infected persons, pollution with intestinal discharges
is not only the most offensive but by far the most
dangerous kind of pollution to which water supplies
are exposed.

"Compliance with the requirements herein recom-
mended will insure a quality of water supply equal to
that of municipal supplies which have been demon-
strated by experience to be entirely safe and satis-
factory, and will at the same time impose no great bur-
den upon common carriers, since it is entirely practi-
cable with moderate direct expense and pains to purify
water to the degree required."

A comment which may be made upon this report of the Treasury Commission is that, while the standard they set is proper under the conditions for which they place it, that is, a single standard for the testing of large varieties of water from different unknown sources, and will give practically a safe water under any such conditions, a somewhat more liberal standard might well be applied in the case of a municipal water supply where the source of the water is known and its possibilities of being subjected to pollution can be investigated on the ground. Under these latter conditions a higher B. coli content may be well in accord with a good and wholesome water.

INTERFERENCE WITH THE PRESUMPTIVE COLI TEST BY OTHER SPECIES OF BACTERIA.

For some time it has been known by bacteriologists that B. Welchii, B. enteritidis, and some other streptococci interfere with the so-called presumptive bile test for B. coli. The details of the discussion concerning these complications are beyond the scope,

bacteriologically, of this address. It is sufficient to state that they are serious and that they require far more consideration than was thought to be the case a few years ago.

It appears that B. Welchii and some other forms of bacteria grow anaerobically and ferment nutrient carbohydrate solutions, although they may not grow on aërobic plates.

Columbus Experiences.—One of the most striking experiences which have come to the attention of the speaker was noted a week or two ago in connection with the operating of the filtering and softening plant of the water works of Columbus, Ohio. This plant, skilfully operated under the charge of Mr. Charles P. Hoover, deals with very hard water during the autumn months. Lime and soda are added to soften it, and as a result large quantities of gelatinous, flocculent precipitate of basic carbonate of magnesia are formed. This brings about a very high degree of bacterial removal as an incident to the softening process and prior to filtration. In a single week there were five days on which numerous samples of the softened and filtered water showed in no instance any bacteria either on gelatine plates or agar plates cultivated either for forty-eight hours at 20° or twenty-four hours at 37°. By ordinary procedures the filtered water was sterile. Yet in fully half the samples of this sterile water positive results were found by the presumptive test for B. coli when 10 cubic centimetres of water were employed.

During the past autumn similar results, but less strikingly frequent, have been noted in connection with the operation of the softening and filtration plant of the water works at Grand Rapids, Mich., and the filtration plant at Evanston, Ill.

At Columbus the bacterial flora of the Scioto River water have been studied with unusual care by Messrs. Copeland and Hoover, who in the Journal of Infectious Diseases, vol. 8, p. 241, 1911, contributed an important paper on "The Interpreta

tion of Tests for B. Coli Communis."

The concluding paragraph of this paper is of much practical importance to water works officials having the responsibility of caring for the quality of municipal water supplies:

'B. coli is found in sewage, and therefore its presence is significant; but, as newspaper reporters and other persons are inclined to magnify conditions, the VOL. CLXXX, No. 1075-4