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61
nutrient media ordinarily employed by bacteriologists is not the most suitable kind of pabulum for
them. It is to be noted as possibly affording some support to this view that if sewage be centrifugalised
and the deposit stained* the microbes taking the stain are not, as might have been
anticipated, chiefly bacillary in form, but appear either as cocci or rods, so short and rounded at
their ends as to simulate cocci. Moreover, these cocci are frequently arranged in long chains (streptococci).
Nevertheless, it may be said with a fair measure of confidence that some, at all events, of
the streptococci in sewage and in sewage effluents are delicate germs, and readily lose their vitality
and die.
The importance to be attached to these observations is great. If in the bacterial treatment
of sewage micro-organisms of presumably feeble vitality pass through the coke-beds in practically unaltered
numbers, then there is every reason to fear that those microbes which we know are distinctly
pathogenic to man, and which may be either habitually present in sewage or present as chance and
occasional visitors, and some of which are believed to be in comparison hardy germs, would likewise
be unaffected by the biological processes at work in the coke-beds.
In previous Reports I have stated "that the balance of evidence points to the probability that
some, at all events, of the pathogenic organisms are crowded out in the struggle for existence in a
nutritive medium, containing a mixed bacterial flora, their vitality being weakened or destroyed by the
enzymes of the saprophytic species." This broad statement was permissible then, but now, in the light
of these results, it can hardly be considered altogether satisfactory.
Lastly, as regards the source of streptococci, it has been said that they are present in the
intestinal discharges of animals, and are absent from waters and soils except in cases of recent and
objectionable pollution. It might perhaps be argued that streptococci may have a wide distribution
in nature, and if so that their presence in a substance, be it soil or sewage or water, is of little
or no significance. Against this view it may be pointed out that if they are delicate germs it is
unlikely that they would survive, much less multiply in nature unless the conditions were ideally
favourable. Further, that although I have frequently isolated streptococci from as minute a
quantity of sewage as .001 c.c., and of human fæces as 0.001 gramme, I have repeatedly failed to
demonstrate their presence in comparatively large amounts of pure water and pure soils.||
These facts have led me to advocate this test (presence of streptococci) as a valuable one in
the bacterioscopic examination of waters.† Not, indeed, that the absence of streptococci implies
"safety," but that their presence affords strong evidence of reeent and therefore presumably
specially dangerous pollution.
In conclusion I venture to assert that this test is of extreme (value in judging sewage
effluents from the biological point of view. And I am strongly of opinion that if an effluent
contains streptococci in practically unaltered numbers, or even in reduced numbers where such
reduction is only in the same proportion as the other microbes also present are reduced, then such
an effluent is, as regards danger to health, no better in the first case than raw sewage and no safer
in the latter than crude sewage slightly diluted, but otherwise unaltered in its possible capacity of
giving rise to disease.
The following is a description of some of the streptococci isolated from London crude sewage
and from the effluents from the bacterial beds.
1. Name—Streptococcus I.
2. Source—1/1000 c.c., Crossness crude sewage.
3. Date—November 16th, 1898.
4. Morphology—Stains well by Gram's method. The chains of cocci are usually short.
5. Plate cultures (under a low power, Leitz, 3 objective, 1 ocular)—
(a) Agar (37° C.)—Small transparent colonies showing wavy granulation. The colonies are
irregular in shape, and at the edges the loops of cocci can be made out§.
(b) Gelatine (20° C.)—Small transparent colonies, circular in shape, and faintly granular.
The edges are clean and no loops of cocci are visible. No liquefaction.
6. Streak cultures—
(а) Agar (37° C.) Small transparent colonies, faintly granular.
(b) Gelatine (20° C.)—A white, transparent film-like growth, which on close observation is
seen to be made up of separate colonies. No liquefaction occurs.
7. Gelatine at 37° C.—No diffuse cloudiness. Flocculent little masses with cirrhus-like extensions.If
8. Broth cultures (37° C.)—The broth remains quite transparent. Flocculent masses with cirrhuslike
extensions are formed in the fluid. Old broth cultures show at the foot of the tube a white granular
mass, the medium itself being quite transparent. On shaking the tube, granular masses of various sizes
rise in the clear liquid and rapidly subside again to the bottom.†
9. Litmus milk cultures (37° C.)—Strong acidity and solid clot in 24 hours.
10. Remarks—A mouse inoculated subcutaneously with 1 c.c. of broth culture remained apparently
unaffected.
1. Name—Streptococcus II.
2. Source—1/1000 Crossness 6 ft. primary coke-bed effluent.
3. Date—November 16th, 1898.
4. Morphology—Stains well by Gram's method. Very short chains as a rule, but occasionally a
chain of medium length may be found.
* Deposit upon the coke in the coke-beds. (Supplement to the Second Report.) See also Plate II., Figs. 6,
7, and 8 of this Report.
║ I have, however, found streptococci in abundance in waters and soils recently polluted with sewage.
† Report of the Medical Officer, Local Government Board, 1898-99.
§ Plate IV., fig. A. (a). ¶ Plate IV., fig. B. (a). ‡ Plate IV., fig. B. (b).