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35
It is notorious that large populations have been exposed to the
poisonous emanations of decomposing- animal substance for a long time
and escaped zymotic disease until, as some allege, the germs of the
disease were accidentally introduced, and their rapid multiplication
promoted by the decomposition; or until, as others allege, a certain
stage of decomposition in these animal matters allowed the infectious
agencies (chemical) to come into operation. Be that as it may, it
would be agreed that there is a great preventative which should be
secured, and that is a free circulation of air through the ground to
dissipate and destroy, by oxidation, the poisonous agencies, be they
gases or other substances. And it is therefore of the utmost importance
in the vicinity of dwellings, and in towns especially, to keep the surface
soil dry so as to let the air circulate freely through the pores of the
soil, where, as in charcoal, oxidation is promoted by the substances
and the air being brought by the extremely fine subdivisions in
molecular contact with one another; thus soil proves a most powerful
disinfector. To secure this circulation of air in the soil and disinfection,
the owners of dwellings have been required to pave their yards with
impervious substance so as to keep the ground dry (I need not say
water excludes the air) and, when this could not be done, the area
being too great, the owners have been encouraged to turn the ground
over so as to let the air and sun's heat pass freely into it. And when
we consider that a house, with its warmer air ascending, acts as a large
exhauster, drawing, so to speak, the air and vapour from the soil situated
under and near the house, towards, and into itself, it is obvious that no
effort should be spared to keep the soil dry and porous, so that immense
quantities of air may be passed through the ground to dilute and destroy
the poisonous substances before they reach the interior of the dwellings.
That gases may thus travel very many feet through the soil and
penetrate into a house is unquestionable. As a distinguished German
Hy gienist says, "Remarkable testimony as to the permeability of the
ground and of the foundations of our houses, has been given by gas
emanations into houses which had no gas laid on. I know cases
where persons were poisoned and killed by gas, which had to travel for
twenty feet under the street, and then through the foundations, cellar
vaults, and flooring of the ground-floor rooms. The house being