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experiments that it has been well substantiated that not only in the act of
coughing and sneezing, but also in loud speaking, fine droplets of mucus are
sprayed from the mouth into the air, that thev float in the air, and that they
may be wafted by air currents, such as obtain in ordinary rooms, to a distance
that at first sight appears to be almost incredible. Thus it has been shown
that by reading aloud for half-an-hour Bacillus prodigiosus may be disseminated
from the mouth to a distance of 24 feet in front, and may also be obtained in the
air behind the speaker. In another experiment by sneezing 12 times, giving a
few short coughs, and speaking a few words, the same bacillus was shown to
penetrate to a distance of 40 feet in front (Kceniger). The length of time these
droplets remain suspended in the air is uncertain ; thus Von Weismayr states
that they fall to the ground within half-an-hour; Kceniger within 1| hours;
while Fliigge believes they may not disappear from the air of the room for 4-6
hours. Now this subject is of serious moment when considered in the light of
phthisis, for there is no reason to suppose, if the Bacillus prodigiosus
spreads to such a distance, that Koch's bacillus would not spread to an equal
distance under similar circumstances and would become a source of infection.
We know that animals have succumbed to anthrax after exposure
for 10-15 minutes to an atmosphere impregnated with anthrax spores
(Buchner in Annales d' l'Institut Pasteur, January 1888) and also that
inhalation experiments with dried tubercular sputum, carried out by
various observers have had positive results; and Koch showed that
tubercular bacilli in pure culture could produce similar results when
inhaled by animals. Other experimenters, Moller, Fliigge, and Heyman, have
shown that when they exposed guinea pigs close to the mouth of coughing
phthisical patients, a proportion of the animals developed tuberculosis. In
this connection it may be recollected that Klein showed that tuberculosis was
contracted by guinea pigs that were kept in a ventilating shaft at the Brompton
Hospital.
We have seen how the Italians and the Spanish in years long
gone by recognised the infective power of the disease although they did
not, as we do, know its real cause. They were not aware, as we are, that
the cough-sprayed minute droplets which are discharged by the patient become
the very finest form of tubercular matter, and may become potent factors in
spreading the disease. Nevertheless, they adopted preventive measures, which
are models to us to-day, with all our accumulated knowledge, and which
are too much ignored or neglected by many sanitary authorities, who, instead
of being apathetic, should be energetic in preventing this frightful scourge of
phthisis, which is so eminently a preventable disease.