182 THE AMERICAN MONTHLY [July 
attempted to imitate nature. But we can not imitate all 
the conditions under which the organism may exist in na- 
ture, and we ought not, therefore, to apply the experience 
of the laboratory too literally to the life history of the 
plague bacillus outside of the body. We may determine 
with fair certainty the length of time the bacillus may 
live under given conditions. But these conditions are more 
or less arbitrary, and to a certain extent artificial. In 
general terms, we can state whether it is a hardy organ- 
ism, resistant to influences usually detrimental to bacte- 
rial life, or one that loses its virulence and dies quickly 
when removed from its natural habitat. The bacillus of 
plague does not exist in nature on sterile glass-cover 
slips, nor yet in the desiccator over concentrated sulphu- 
ric acid, which were conditions used by some authors who 
have reported their results on this question. 
The test objects were very abundantly inoculated with 
a pure culture of the bacillus pestis of known activity and 
virulence. Often the test objects were saturated. The 
cultures had been grown for a long time upon artificial 
media in the laboratory, so that their vitality was prob- 
ably strongly influenced. .It is a well-known fact that 
virulent pathogenic bacteria may at first grow very poor- 
ly upon the ordinary laboratory media, but by successive 
cultivation they become accustomed to the new conditions, 
so that they finally thrive abundantly ; that is to say, they 
take on a sort of saprophytic existence. Such cultures 
would doubtless resist the various influences to which 
they are exposed in the laboratory tests better than an- 
other race direct from the blood or tissues. In fact, it is 
found that the plague bacillus in the blood and tissues 
from a rabbit usually dies out rather quickly when dried 
upon the test objects. On the contrary, bouillon cultures 
dried on similar objects and under similar conditions live 
a much longer time. | 
Another departure from normal conditions was the fact 
