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60
Thus although the effluents usually contained fewer bacteria and less of B. culi and spores of
B. enteritidis sporogenes than the crude sewage, the reduction was not well marked, and, indeed,
was immaterial from the epidemiological point of view, considering the actual number still
remaining. For, as has been already pointed out, the effluents usually contained more than one
million microbes, more than 100,000 B. coli, and at least 100 but less than 1,000 spores of B.
enteritidis sporogenes per c.c.
IV.—STREPTOCOCCI IN THE BARKING AND CROSSNESS CRUDE SEWAGE
AND IN THE EFFLUENTS FROM THE BACTERIAL COKE-BEDS.
In the First Report* under the heading of "Methods" it was stated that streptococci and
staphylococci were to be looked for in agar cultures incubated at blood-heat. In the Second
Report† when dealing with the "species of micro-organisms" it was noted that streptococci and
staphylococci were present both in the crude sewage and in the effluents from the coke-beds. In
the present Report it is proposed to give the results of the work carried out in this direction. It
is to be noted that the records extend back to November, 1898.
Although attention was directed to the study of staphylococci as well as streptococci it is the
latter class of germs which will be considered here. One reason why staphylococci are considered
of relatively less importance than streptococci in connection with the work is that the former as a
class are hardy germs, whereas the latter as a class are delicate micro-organisms. The b aring of
this remark will be shown presently.
My chief reasons for considering this portion of the sewage inquiry of special and peculiar
importance are briefly as follows—
Speaking of streptococci as a class it may be said that—
(1) They are among the most pathogenic of all the bacteria which are at present
known;
(2) They are delicate germs, and very readily lose their (vitality and die;
(3) They are present in the intestinal discharges of animals. In human fteces there
may be more than 1,000 present in one gramme;
(4) They are absent from water and soil ,§ except in those cases where there has been
recent contamination with sewage or other substances equally objectionable in character.
It will presently¶ be shown that both in crude sewage and in effluents from coke-beds
streptococci are present in great abundance—usually more than 1,000 in 1 c.c.—and that the
bacterial treatment of the raw sewage effected no marked alteration in their numbers.
Now if the streptococci found in such numbers in the crude sewage and in the effluents are derived
from the intestinal contents of animals, and are delicate germs, and are also pathogenic, the position
is a somewhat serious one.
In the first place, as regards experiments on animals, the records show that the streptococei
were more often non-pathogenic than pathogenic in the case of mice. Numerous records of the
effects on mice of streptococci isolated from soil-polluted water, sewage, and sewage effluents which
I have since obtained and which are not included in this Report show that as a rule, and when
obtained from the above sources, they are not pathogenic. Still it must not be lost sight of that
the absence of pathogenic effect on mice does not necessarily imply the absence of diseaseproducing
property in other animals. Nor does it prove that the streptococci were previously nonpathogenic.
Further, it is conceivable that some alteration in the conditions surrounding these
streptococci might, if they had been pathogenic in the past, restore to them all their original
virulence.
Speaking in general terms, however, it may be said that the streptococci found in nature
outside the animal body, e.g., in polluted soils and water, in sewage and sewage effluents are not
as a rule pathogenic to mice.
Secondly, as regards the assertion that streptococci are delicate germs and readily lose their
vitality and die. Although this certainly accords with our experience of streptococci isolated
from the human subject, particularly in cases of disease and septic infection, it might well be the
case that some at all events of the streptococci occurring in nature outside the animal body, e.g., in
sewage, are hardy germs and are capable not only of resisting death, but also of multiplying under
favourable conditions. In all probability this is true to some extent, yet it is not without significance
that certain of the streptococci about to be described when subcultured in gelatine and
incubated at 20° C. showed little or no appreciable growth at the end of thirteen days. And some
of the streptococci that I have isolated from sewage-polluted water, etc., have proved their delicacy
by refusing to grow when subcultures were not carried out at short intervals. Thus on several
occasions the study of a streptococcus has been prematurely cut short by the death of the organism.
Still further it has been a matter of common observation that subcultures made from colonies in
agar plate cultures of sewage which (colonies) under a low power of the microscope revealed their
real nature by the occurrence of separate loops of cocci at the periphery, frequenily showed no
growth, the microbes (streptococci) having already lost their vitality. In opposition to this it
might be urged that certain of the streptococci in sewage are in reality hardy germs, but that the
* Filtration of sewage (First Report), page 3, B. 6 (e).
† Bacterial treatment of crude sewage (Second Report), page 27, III., 4 (c).
§ The significance of streptococci in water and soil is dealt with by me in Reports to the Local Government
Board. Report of the Medical Officer, Local Government Board, 1898-9.
In this and succeeding paragraphs I purposely anticipate what follows.