PRELIMINARY NOTE 
ON THE 
VIABILITY OF THE BACILLUS PESTIS. 
M. J. Eosenau, Passed Assistant Surgeon, and Director of the Hygienic Laboratory, 
United States Marine-Hospital Service. 
There seem to be three factors that influence the life of the bacillus 
pestis in the outer world, viz, light, moisture, and temperature. The 
bacillus withstands quick drying very badly, as all the experiments in 
this direction indicate. It can not live long in the sunshine. High 
temperatures are invariably fatal. 
That it always and under all circumstances dies in so short a time as 
five days, as the work of Kitasato and Wilm first indicated, must now 
be doubted in view of the experience of Abel, Ficker, Batzaroff, Han- 
kin, The German Plague Commission, Germano, Giaxa, and myself. 
The bacillus of plague does not exist in nature on glass cover slips, 
nor yet in the desiccator over concentrated sulphuric acid. With us it 
certainly would not be exposed to drying in our houses, and on fabrics, 
at temperatures of 30° and 37° G., conditions under which many of the 
tests to determine the viability of the organism were made. 
We ought, therefore, not to apply the experience of the laboratory 
too literally to the life history of the plague bacillus in nature, for we 
can not imitate all the conditions under which the organism may exist. 
We may determine with fair certainty the length of time the plague 
bacillus may live under given conditions ; and in general terms we can 
' state whether it is a hardy organism, resistant to influences usually 
detrimental to bacterial life, or one that loses its virulence and dies 
quickly when removed from its natural habitat. 
In this laboratory we have worked with the organism from 5 sources, 
1 from Djiddah, 1 from Oporto, 1 from Eio de Janeiro, 1 from Bombay, 
and 1 from the New York quarantine case. We find that all these 5 
races thrive well under the usual laboratory conditions on the ordinary 
media. 
They can in no sense be considered tender organisms, as was at first 
supposed. They are much easier to cultivate than the lanceolate coccus 
of pneumonia or the streptococci. In fact, they resemble more closely 
the hardier of the hemorrhagic sfepticccmic group. 
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