View report page

4
DIVISION II—BACTERIOLOGICAL.
BY
A. C. HOUSTON, M.B., D.Sc.
Notes on the Deposit upon the Coke in the Coke-beds.
On May 11th, 1899, samples of coke from the Barking bed were submitted to examination.
The coke was found to be coated with a black-coloured slimy deposit, free from objectionable
smell, and almost odourless. The deposit, which was readily detached from the surface of the
coke, was examined. When looked at under a low power of the microscope it was found to be
composed largely of minute particles of coke and sand,* together with, apparently, imperfectly
disintegrated animal and vegetable matter. This organic matter is probably of such a nature as to
resist the action of bacteria for a very considerable time, if not almost indefinitely.
Infusoria, diatoms and minute worms of different kinds were present, but the sewage fungus
was not observed to be present to any extent.
A portion stained with the usual aniline dyes (gentian violet, methylene blue, &c.) showed
that bacteria (reacting to such stains) were not present in the number that might have been
anticipated.
On diluting the deposit largely with sterile water and making cultures therefrom, it was
found that the number of bacteria per gramme of deposit was 1,800,000. This number of microbes,
large as it may appear, would weigh only a minute fraction of a gramme, so that it is evident that
the number of living bacteria do not in themselves account in any way for the deposit. The writer
has made experiments on this subject and has found that 1,800,000 typhoid bacilli weigh only
0'0000147 gramme.
The number of spores of B. enteritidis sporogenes was found to be at least 10,000, but less
than 100,000 per gramme of deposit.
The character of the microbes appearing in the cultures differed somewhat from those found
in crude sewage. For example: There was an increase in the number of spores of B. enteritidis
sporogenes (Klein), and a decrease in the number of B. coli. Proteus-like germs were present in
abundance; many being of P. mirabilis type. Further, B. arborescens and an allied form were
present in considerable numbers. An organism apparently identical with B. prodigiosus was also
isolated. It is perhaps worthy of note that a guinea-pig inoculated with some of the deposit
developed an abscess at the site of inoculation, and when this abscess was opened some weeks later
the same characteristic red-colour-forming bacillus was among others isolated from the pus.
Two mice, inoculated subcutaneously with a small portion of the deposit, died with all the
characteristic symptoms of tetanus. Microscopic cover-glass preparations were made from the
seat of the wounds: numerous bacilli showing drum-stick spore-formation, and indistinguishable
from bacillus tetani, were noted. A pure cultivation of the tetanus bacillus was not obtained, but
two anaerobic microbes showing terminal spore-formation were isolated from the seat of the wound.
One of these liqufied gelatine, the other did not. They appeared to be identical with two microorganisms
isolated by direct anaerobic culture from soil by the writer. +
It has been stated that when the deposit was stained with the aniline dyes ordinarily in use
only a limited number of bacteria reacted to the stain. But in addition to ordinary staining, specific
staining was resorted to, and with the following results—
The deposit was mixed with sterile water, and cover-glass preparations were made. These were
stained with hot carbol-fuchsin, thoroughly decolourised in 33 per cent. nitric acid, and counterstained
with methylene blue. It may here be explained that this is the specific staining reaction for
the tubercle bacillus, and that all other organisms except tubercle, are stained blue by this method,
the tubercle bacillus alone resisting decoloration with the acid, and therefore alone retaining the
bright red colour of the carbol-fuchsin stain. There are, however, a few exceptions to this rule,
namely, the leprosy bacillus, and certain other organisms (some pathogenic, others non-pathogenic)
of recent discovery in milk, fatty and other matters, which the Germans have called "acid-fast"
bacteria.
Now on staining in the above manner a large number of cover-glass preparations
of the deposit, it was found that a considerable number of bacteria retained the red stain after
treatment with 33 per cent. nitric acid. Moreover, many of these bacteria were indistinguishable
morphologically from the tubercle bacillus, and were frequently arranged in small
clumps. Some, however, were shorter and plumper, and others took the red stain more deeply
than the tubercle bacillus. Nevertheless, the fact remains that in specific staining reaction, in their
arrangement in little clumps, in their appearance as small thin beaded and curved rods, some of
the bacteria resembled the tubercle bacillus so closely as to suggest a similarity of species.§
It does not follow from the above that these microbes, whatever their nature, were alive,
for micro-organisms which have lost their vitality may nevertheless react to stains. Yet, on the
other hand, it might well be the case that while the majority were dead some still retained their
vitality, and it might even be true that they were capable not only of remaining dormant, but also
of multiplying in the coke-beds.
Before proceeding to describe certain experiments carried out on animals, it is of advantage
* See fig. 1.
† Ed. Med. Journal, Nov., 1893.
§ See figs. 2, 3, 4, 5, and 7.