London's Pulse: Medical Officer of Health reports 1848-1972

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London County Council 1900

[Report of the Medical Officer of Health for London County Council]

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Table I.—Showing the remit of exposure of the bacillus typhosus to formalin vapour.

Nature of emulsion in which the typhoid bacillus was exposed.Nature of the material on which the emulsion had been placed.Result of culture after exposure.
Broth emulsionWood+
(Separated) milk emulsionWood
„ „Cloth
,, „Linen
„ ,,Paper
Melted gelatine culture allowed to setWood
„ „ „Cloth
„ „ „Linen
„ „ „Paper

2.—Bacillus diphtheriœ.
Experiment A.—Emulsion of bacillus diplitheriæ from a 24 bour old agar culture in
separated milk was liberally applied to wood, linen, cloth and paper, and, after drying, exposed
to formalin in the same place and under exactly the same conditions as in previous experiments.
One control diphtheria paper was kept (24 hours) till the exposed materials were ready,
after disinfection, to be used for culture. All these materials were placed in broth in test tubes
and incubated at 37° C. After this time only the broth inoculated with the control diphtheria
paper and from the disinfected diphtheria wood, were found turbid. Agar surface plates were
made and these were kept for 24 hours at 37° C. The agar plate of the diphtheria wood was
covered with a film of bacillus mesentericus, the agar plate of the control diphtheria paper
showed numerous diphtheria-like colonies. These were tested by microscopic specimens, by
Neisser's stain, and by injection in guinea pigs, and found to be typical virulent diphtheria,
the same as was applied originally to the paper.
This experiment proves, therefore, that while the diphtheria bacilli, dried on paper in
the laboratory for 24 hours, remain living, those exposed on wood, cloth, linen and paper to
formalin for 5 hours became completely disinfected and killed.
Experiment B.—This experiment was of the same nature as the former, except that the
diphtheria bacilli were applied to the materials as a (liquefied) gelatine culture incubated for
24 hours at 37° C. The result was also negative, inasmuch as none of the materials after
exposure to the formalin yielded diphtheria growth

The following table II. gives a summary of the results—

Nature of the emulsion.Nature of the materials.Result of culture after exposure.
Separated milk emulsionWood
„ „Cloth
„ „Linen
„ „Paper
(Melted) gelatine cultureWood
„ „Cloth
„ „Linen
„ „Paper

In both experiments, therefore, the 5 hours' exposure to formalin was effective in completely
destroying the bacillus dipbtherise on all the four materials employed.
3.—Bacillus pyocyaneus.
Experiment A.—The emulsion of this organism was made in separated milk, the materials,
wood, cloth, linen and paper were charged liberally with the emulsion, and then, after drying
in the air of the laboratory, were exposed to formalin in the same manner as in previous experiments.
The result was that the microbe was disinfected and devitalised on all four materials;
the broth cultures that received the materials after the treatment with the formalin yielding no
pyocyaneus growth.
Experiment B.—The former experiment was repeated with hot gelatine culture, i.e., the
microbe was grown in gelatine at 37° C. for 24 hours, and then this was applied to the surface
of the materials. The result of exposure to the formalin was the same as in the previous experiment,
viz., complete disinfection.
The following table III. shows these results—