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67
1. Name—Streptococcus XXI. '
2. Source—1/1000 c.c., Barking crude sewage.
3. Date—November 1st, 1899.
4. Morphology—Stains well by Gram's method. The chains of cocci are usually short, but
occasionally long chains may be seen.*
5. Plate cultures (under a low power, Leitz, 3 objective, 1 ocular)—
(a) Agar (37° C.)—Minute, transparent, faintly granular-looking colonies with clean edge.
Usually circular in shape.
(b) Gelatine (20° C.)—Small transparent colonies showing only very faint granulation.
Colonies are circular with slightly wavy border. No liquefaction.
6. Streak cultures—
(a) Agar (37° C.)—No record.
(b) Gelatine (20° C.)—Resembles Streptococcus XIX. and XX., but the colonies are smaller
and more transparent-looking.
7. Broth cultures (37° C.)—Abundant diffuse cloudiness; at foot of tube viscous white deposit.
8. Litmus milk cultures (37° C.)—Strong acidity, but no clot.
9. Remarks—A mouse inoculated subcutaneously with 1 c.c. of broth culture was apparently
unaffected.
General Summary of the above results, as regards the presence of Streptococci in the
Crude Sewage and in the Effluents from the Bacterial Beds.
Name—It is apparent that many of the streptococci resembled S. Brevis and some
S. Longus. Moreover, certain of them, if they had been isolated from a septic case
in the human subject, would almost certainly have been classed as S. Pyogenes.
In the present state of our knowledge, it has been thought best to merely register
them for descriptive purposes as Streptococcus I., II., III., &c. Of course, many
of them resembled each other so closely as to suggest identity of species or, at
all events, close kinship. But the results seem to indicate that streptococci are
not only more numerous, but that the number of different species is much greater than
has hitherto been supposed. A great many microbes isolated from crude sewage and
effluents from bacterial beds are not included in the above list, because, on studying
their morphological and biological characters, they seemed to resemble staphylococci
(a class of germs as numerous in sewage apparently as streptococci, but probably of
relatively less importance) more closely than streptococci. The line, however, dividing
these two classes of germs is by no means a sharp one, and it is possible that a few
microbes have been included in the above list which really ought to be placed in an
intermediate position, i.e., between the streptococci and staphylococci.
Source—In each case the streptococci were isolated from as minute a quantity as
1/1000 c.c. of Barking or Crossness crude sewage, or the effluents from the coke-beds at
Barking and Crossness. There did not appear to be any significant alteration in the
number of streptococci as the result of the bacterial treatment of the raw sewage.
Date—It is to be noted that the earlier records extend back as far as November,
1898.
Morphology—All stained well by Gram's method. The majority formed short
chains, but in some the chains were of medium length, and in a few the chains were
long. Sometimes the chains cohered together forming masses, thus simulating staphylococci.
In such cases the biological characters of the microbes were closely studied
before coming to a definite conclusion. [As a rule staphylococci grow more rapidly
and produce a much more luxuriant and opaque growth on the surface of gelatine and
agar than streptococci. Further, staphylococci not uncommonly liquefy gelatine. On
the other hand, streptococci do not liquefy gelatine, and as a rule grow very slowly
and form minute and transparent-looking colonies in agar and gelatine cultures.]
Temperature—It is to be noted that all the streptococci grew well at blood heat.
Agar and gelatine cultures—In most cases the colonies were very small, circular in
shape, transparent-looking, and faintly granular, with ,a clean edge. Sometimes,
however, the colonies showed coarse, wavy granulation, and were irregular in shape
with a frayed edge, or showed at the periphery separate loops of cocci. It must not be
lost sight of that some of the streptococci showed little or no appreciable growth when
incubated at 20° C. for 13 days in gelatine streak culture.
Broth cultures—About 50 per cent. produced diffuse cloudiness with a viscous
white deposit at the foot of the tube. In about 20 per cent. the broth remained quite
clear, the growth appearing either as a conglomerate mass or else as masses with
cirrhus-like extensions. In about 15 per cent. the cloudiness was granular in character
with streaky cirrhus-like growths. In about 10 per cent. there was diffuse cloudiness
* Plate I., fig. 4.