4 
In this connection, Batzaroff (a) states: ^‘It may be said that it is a 
mistake to consider the microbe of human pest to be very frail. There 
undoubtedly exist varieties that attenuate very quickly, and die outside 
the living body in a relatively short time. There are other varieties 
that retain their viability under similar conditions a long time, and 
continue to live in artificial media for months and even years without 
notably losing virulence. We have seen that certain of our cultures 
which have been kept in the laboratory without any precautions and 
exposed to the light for three and one-half months, still kill animals 
when injected hypodermatically with but slight retardation; and that 
regenerated 2 or 3 times they almost regain the virulence they first 
possessed. It is not always easy to obtain an attenuated culture of 
pest. It requires much time and a combination of various artifices.’’ 
On first glance over the literature on the viability of the organism 
there appears to be an irreconcilable difference among the various 
observers as to the length of time the organism will live and maintain 
its virulence outside the body, but on closer study it becomes apparent 
that these differences are due to different conditions under which the 
experiments were carried out, especially differences in temperature. 
We must not lose sight of the fact that some races of the organism are 
more hardy than others. 
It is the experience of all observers that the bacillus can not live long 
outside the body when dried at a temperature of 30° C., or over, but at 
a temperature lower than this and under 20° 0. , it has been kept alive 
sixty and seventy-five days. 
The German Plague Commission (b) found that the organism always 
lost its power of infection when dried, within eight days, in India, but 
after returning to Germany could be kept alive after drying twenty- 
eight days, at 15° to 18° C. 
My own experience indicates that the organism, when dried, will 
die quickly if the temperature reaches 27° C. but that at 23° 0. and 
under it may live a long time. 
A series of experiments has been undertaken in this laboratory and 
a few of the results are given in advance showing how long the 
organism may live and retain its virulence when dried under various 
conditions. 
ALBUMIN- GELATIN BALLS INFECTED WITH PLAGUE CULTURE. 
A little ball of sterile absorbent cotton about the size of a pea is soaked 
with a few drops of a gelatin culture of plague (Djiddah) mixed with 
egg albumin, and exposed in a Petri dish in the photographic dark room 
(20° to 23° C.) and the cool chamber (17° to 19° C.). 
a Batzaroff La Pneumonie pesteuse experimentale. Annales de I’Institut Pasteur^ 
May, 1899, page 391. 
SKaiserliche Gesundheitsamt, Bd. 16, Berlin 1899, page 274, et seq. 
