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56
(d) Concluding Remarks.
On November 1st, 1899, B. pyocyaneus* was isolated from 1/1000 c.c. of the effluent from the
second coarse bed (series A). It was very virulent, 1 c.c. of a 24 hours broth culture killing
a guinea-pig in less than 24 hours. The same micro-organism was isolated in pure culture from
the heart's blood, etc., of the animal. (See fig. 5, Plate II.)
On December 6th, 1899, three strains of "sewage proteus" were isolated from 1/10000 c.c.. of the
effluent from the primary coarse bed (series B). They all liquefied gelatine very rapidly, they were
actively motile, and produced "gas" in 24 hours in gelatine "shake" cultures. One of the strains
killed a guinea-pig in 24 hours (1 c.c. of broth culture); another was not so virulent, ulceration
occurred at the site of the inoculation, and the animal recovered; the third produced only a slight
local reaction. This latter non-virulent strain of "sewage proteus" was used to inoculate the 13-feet
coke-bed at Crossness (see page 75).
On November 1st, 1899, streptococci xix., xx., and xxi., were isolated from 1/1000 c.c.
respectively of the effluent from the primary coarse bed (series A), the effluent from the secondary
coarse bed (series A), and the crude sewage. (See pages 66 and 67.)
During a considerable period of the enquiry, attention was directed to the study of the
thermophilic bacteria. It was suggested to me, by Dr. Gordon, that a comparison of their numbers in
the crude sewage and effluents might be of value.
These micro-organisms (B. thermophilus and its allies) have been shown to be present in the
alimentary canal of human beings and mammals, in sewage, in sewage-contaminated waters, and in
soil, but not in pure waters.
It was found that thermophilic bacteria § (capable of growing luxuriantly in broth culture at a
temperature of 60-70° c.) were present in London crude sewage in abundance. They were also
present, although usually in smaller proportion, in the effluents from the coke-beds.
It has been suggested that the presence or absence of these bacteria in a water supply might
be employed as a test of potability. But, in my experience, thermophilic bacteria are present in
numbers in soils not recently polluted and are often absent from waters known to be freshly contaminated
with objectionable matters, waters, moreover, which, by more reliable and delicate
bacteriological tests, can readily be shown to be dangerously polluted.
Certainly the presence of thermophilic bacteria in a water would lead one to suspect gross
contamination, but their absence could hardly be regarded as testifying to purity or "safety."
Nevertheless, the test, as a rough indication of the probable biological quality of a liquid and
as a means of comparing different liquids, e.g., crude sewage and bacterial effluents, is one not devoid
of value.
III—THE EXPERIMENTS ON BACTERIAL TREATMENT AT CROSSNESS.
1.—FURTHER EXPERIMENTS WITH THE EFFLUENTS FROM THE 4-FOOT, 6-FOOT
(PRIMARY), AND 6-FOOT (SECONDARY) COKE-BEDS AT CROSSNESS.
In the Second Report the bacteriological results were brought up to the end of December, 1898.
In the early part of the year 1899 some further experiments were carried out with the effluents from
the 4-foot, 6-foot (primary), and 6-foot (secondary) coke-beds. These took the form of comparative
determinations of the number of spores of anaerobic bacteria in the raw sewage and in the effluents
from the coke-beds.
Number of Spores of Anaerobic Bacteria in Crossness Crude Sewage and in the Effluents
from the Coke-beds.
The effect of the bacterial treatment of the raw sewage in coke-beds as regards the number of
spores of anaerobic bacteria was to a considerable extent covered by the comparative determinations of
the number of spores of B. enteritidis sporogenes in the raw sewage and in the effluents, carried out
since February, 1898. Nevertheless, it was considered advisable to supplement those records with a
series of experiments dealing with the number of spores of anaerobic bacteria of all kinds in the raw
sewage and in the effluents capable of growing at 37° C. in agar under anaerobic conditions.

The agar tubes were boiled for half-an-hour, rapidly cooled to 80° C., inoculated with the sewage or
effluent, and heated to 80° C. for 10 minutes. The contents were next poured into plates, and these were
immediately placed in an air-tight chamber containing a freshly-prepared mixture of pyrogallic acid and
potassium hydrate solution. These results are shown in graphic form in Diagram 5.
* See fig. 5. This micro-organism (B. Pyocyaneus) must not be confused with the ordinary liquefying
fluorescent bacillus (B. fluorescens liquefaciens) of sewage, soil and water. R. fluorescens liqucfaciens does not
grow, or only imperfectly, at blood-heat, and is not virulent; and differs in a number of other important respects
from B. Pyocyaneus.
§ figs. 9 and 10 show the morphological appearance of B. Thermophilus or an allied form. The microorganism
represented in the micro-photographs was isolated from London crude sewage: it grew luxuriantly at
a temperature of 60-70° C.