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with a deposit at the foot of the tube coherent in granular masses. In about 5 per
cent. a viscous white mass collected at the foot of the tube, the broth remaining
transparent.
Litmus milk cultures—About 85 per cent. produced acidity but no clot. About
5 per cent. showed acidity and clot. About 10 per cent. produced no visible change.
Experiments on animals—Only a limited number of experiments were carried out.
Sometimes a pathogenic effect was produced in mice, but most of the animals were
apparently unaffected. An absence of pathogenic effect as regards mice does not
necessarily imply freedom from disease-producing capability in respect of other animals.
Moreover, some of these streptococci may have been highly virulent in the past, but
have lost their pathogenic action. It is conceivable that these same streptococci might
under certain conditions regain their full virulence.
It is apparent from these results that the type of streptococcus which is especially
abundant in sewage is one presenting the following characters. For convenience of
description it is permissible to call this microbe "Sewage Streptococcus." The following
is a brief description of its chief morphological and biological characters —
1. Name—" Sewage Streptococcus."
2. Source—Barking and Crossness crude sewage and effluents from bacterial coke-beds.
3. Abundance—Usually more than 1,000 per c.c. of crude sewage and effluents.
4. Temperature—Grows well at blood heat.
5. Morphology—Stains well by Gram's method. The chains of cocci are usually short.
6. Agar and gelatine plate cultures (under a low power, Leitz, 3 objective, 1 ocular)—The colonies
are small and transparent. They are nearly circular in shape with a clean edge. The granulation is
faint. The colonies in agar are usually more granular and darker looking than in gelatine cultures. The
gelatine is not liquefied.
7. Streak cultures (agar at 37° C. and gelatine at 20° C.)—The growth usually shows itself as a
delicate white film, which on close observation is seen to be made up of numerous separate minute transparent-looking
colonies. The gelatine is not liquefied.
8. Broth cultures (37° C.)—Abundant diffuse cloudiness. On gently shaking the tube a viscous
white deposit rises from the foot of the tube in a spiral form.
9. Litmus milk cultures (37° C.)—Acidity, but usually no clot.
10. Remarks—Probably non-pathogenic to mice.
It will be understood that the above is a description not of a special micro-organism,
but of the type of streptococcus most commonly present in crude sewage and in the
effluents from the coke-beds.
V.—EXPERIMENTS ON ANIMALS.
Injection of Crude Sewage and Effluents into Guinea-Pigs.
The conclusions which have been arrived at as a result of the above experiments may bo
briefly stated as follows:—
I.—The subcutaneous injection of Barking and Crossness crude sewage into guinea-pigs
(about 1—3 c.c. per 200 grammes weight) always produces a local reaction, and usually death in
from 24 to 72 hours. If the guinea-pigs do not die within the first few days, although
suppuration and ulceration may set in at the site of the inoculation, the animal usually eventually
recovers completely. Sometimes the effluents from the coke-beds are more pathogenic than the
raw sewage itself, but as a rule a somewhat larger dose of effluent is required to produce a fatal
result. If the crude sewage or effluent be injected intra-peritoneally instead of subcutaneously,
the animals usually die more quickly, and succumb to a smaller dose. There are, however,
exceptions to this rule.
II.—If the injection of the crude sewage or effluent is not followed by fatal results within
the first few days, the animal may occasionally die after the lapse of some weeks time, and on
post-mortem examination show appearances simulating tubercle infection; but on closer study
it will be found that death was really due to pseudo-tuberculosis (B. pseudo-tuberculosis of Pfeiffer).
[It will be remembered, however, that in one case a guinea-pig inoculated with a portion of
coke-deposit died from true tuberculosis. Supplement to Second Report.]
III.—When the animal dies rapidly (24—72 hours), virulent microbes, belonging to the
class of B. coli and B. proteus, may readily be isolated from the blood or tissues of the animal.
IV.—If the crude sewage or effluent be previously heated to 100° C. for one hour, large
doses may be injected without producing a fatal result. This would seem to show that the
pathogenic effect of the sewage and effluents is not directly traceable to such of the intra-cellular
and extra-cellular products of microbes as are capable of resisting this temperature.
[This temperature (100° C.) would change poisonous active albuminoids to non-poisonons
passive albuminoids, and would also decompose enzymes ; but it would not destroy the poisonous
substances resulting from the decomposition of putrefying albuminoids known as ptomaines.]
V.—If the crude sewage or effluent be previously heated to 80° C. for ten minutes, a
pathogenic effect may still be produced; but a much larger dose is usually required than where
the liquid has not been so heated. Here death, when it occurs, is probably due to B. enteritidis