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2.—BIOLOGICAL CONCLUSIONS.
Although the total number of bacteria, the number of spores of aerobic bacteria, the number
of liquefying microbes, the number of B. coli and of spores of B. enteritidis sporogenes was, on an
average, less in the effluents from the coke-beds than in the corresponding samples of crude
sewage, the reduction was not well marked, and in some cases the effluents contained more microorganisms
than the sewage before treatment. Thus, while the chemical results were always
satisfactory, the bacteriological results were usually quite the reverse, because the microbes
producing the chemical changes passed through the coke-beds in practically unaltered numbers.
[The reasons for this state of things would seem to be that the process itself depends for
its success on the vital activity of bacteria; that the fragments of coke are not fine enough to
allow of the mechanical separation of the germs ; that the products of the growth of the microbes,
while they are self-injurious, are not sufficiently poisonous to destroy their life, although they,
doubtless, exercise a restraining influence on the extent of the multiplication; and finally, that
purification is not carried sufficiently far to exhaust all the assimilable pabulum in the liquid.
It has been pointed out in previous Reports that B. coli is an aerobic facultative anaerobic
microbe of intestinal origin which may be pathogenic, and that B. enteritidis sporogenes (Klein) is a
pathogenic anaerobe typical of excremental matters which appears to be causally related to certain
cases of acute diarrhoea in the human subject, and whose cultures are extremely virulent to
guinea-pigs.
Both in this and in previous Reports it has been stated that B. coli and the spores of
B. enteritidis sporogenes are present in the effluents from the coke-beds in numbers usually
exceeding 100,000 and 100 respectively per c.c. Further, it has been shown that a proteus-like
germ ("sewage proteus") is present in abundance in the effluents—usually more than 100,000 per
c.c. Some strains of this microbe are very virulent to guinea-pigs. Lastly, a highly virulent
strain of B. pyocaneus has been isolated from so minute an amount as 1/1000 c.c. a Barking
coke-bed effluent.
Further, the cultures made from the crude sewage and effluents were frequently compared
side by side, yet no distinct differences could be made out between the two sets of cultures as
regards the species of microbes.
[Of course this does not preclude the possibility of there having been a failure to detect
points of difference not easily appreciable even to the trained observer. Still less does it mean
that no selective process was in operation in the coke-beds. It is known that certain microbes,
e.g., the nitrifying germs, do not grow on the media ordinarily used by bacteriologists; and no
doubt, as time goes on, the list will be greatly increased. The mere fact that; the raw sewage
contained little or no oxidised nitrogen while the effluents contained nitrites and nitrates, implies that
nitrification was in progress, and doubtless the nitrifying germs were not only stored in the cokebeds,
but were present in the effluents in greater number than in the raw sewage. Indeed,
certain experiments which were carried out in this connection, but which are of too preliminary
a character to merit inclusion in this Report, seemed to support this view.]
In the present Report records are given showing that streptococci presumably of intestinal
origin pass through the coke-beds in practically unaltered numbers, and may be isolated from
1/1000 c.c. or less of the effluents. And reasons are given which suggest somewhat strongly that
if streptococci can resist the biological processes at work in the coke-beds there is small ground for
believing that other germs of a dangerous kind, e.g., the typhoid bacillus, will be destroyed.
Further, it has been stated in this Report that although the products of the bacteria in the
effluents are not fatal even when large doses are injected subcutaneously into guinea-pigs, the
effluents plus the contained bacteria are decidedly pathogenic and do not indeed differ in this
respect materially from the raw sewage.
[A local reaction is always observed, and abscess formation and ulceration frequently result
from the injections, although they do not necessarily prove fatal. When death occurs rapidly, the
fatal result seems to be usually due to virulent B. coli or B. proteus or B. enteritidis sporogenes, or
to microbes more or less closely allied to these germs. Doubtless, however, other microbes are
also concerned in producing a pathogenic effect. Sometimes the animal apparently recovers, but
eventually dies from pseudo-tuberculosis (B. pseudo tuberculosis.)]
In the Supplement to the Second Report it was shown that the deposit accumulating on the
coke in the bacterial beds contained the spores of B. enteritidis sporogenes in great abundance, and
also that two mice inoculated subcutaneously each with a small portion of the deposit died with
all the characteristic symptoms of tetanus. Further, "acid-fast bacteria were present in considerable
numbers in the deposit, and they were also found in the crude sewage and effluents—
particularly in the latter. The inference would seem to be that the "acid-fast" bacteria are stored
in the coke-beds, and are habitually or occasionally washed away in the effluents.
[Although many of these "acid-fast" bacteria could not with certainty be morphologically
distinguished from the tubercle bacillus, it was not claimed that they were necessarily the microbe
of tuberculosis, alive or dead, virulent or non-virulent. But it was pointed out as a significant
fact that in one instance a guinea-pig inoculated with the deposit from a bacterial bed (not,
however, one at Barking or Crossness), especially rich in these "acid-fast" bacteria, did die from
tubercular infection, and that sections of its organs when appropriately stained showed the
presence of numerous tubercle bacilli.]
In view of these results, only one conclusion seems possible, namely, that however satisfactory
the process may be from the chemical and practical point of view, the effluents from the bacterial
beds cannot be reasonably assumed to be more safe in their possible relation to disease than raw sewage
slightly diluted, bud otherwise unaltered in its bacterial composition.