AN INVESTIGATION OF A PATHOGENIC MICROBE 
(B. typhi murium — Danyz) 
APPLIED TO THE DESTRUCTION OF RATS. 
[M. J. Eosenau, Passed Assistant Surgeon and Director of the Hygienic Laboratory, 
United States Marine-Hospital Service.] 
The subject of the destruction of rats has assumed great importance 
within recent times on account of the spread of plague to the four 
quarters of the globe. 
In the short time since 1894, when plague broke from its Eastern con- 
fines where it had slumbered so many years, a great mass of exact 
scientific knowledge has been gathered concerning the disease. The 
relation of the rat to the spread of the disease has especially engaged 
the attention of investigators. 
During the great outbreaks of plague in the middle ages the unusual 
mortality among the rats was noticed, and it was obvious then that these 
animals played some role in the spread of the disease. We now know 
definitely that the rat is susceptible to plague. This rodent sickens and 
dies of the disease in much the same manner as man. An epidemic 
may be foretold by a great increase of mortality in rats, for when this 
occurs it ,may be shown that the rats first contract the disease and 
afterwards transmit it to man. 
The destruction of rats has, therefore, become of the first importance 
from the standpoint of the public health and the prevention of the 
spread of plague. 
Plague has threatened our country from both its seacoasts, and it is 
probable that the only reason it has not spread in San Francisco is due 
to the fact that the disease has not been prevalent among the rats. 
In the spring of 1900, J. Danyz described a new method for the 
destruction of rats by means of cultures of a certain bacillus (a). This 
bacillus he obtained from a spontaneous epidemic among harvest mice 
and by means of rather complicated and artificial methods he managed 
to increase its virulence so that it became pathogenic for the several 
species of rats. The claim is made that the employment of tlie cultures 
a Annales de I’Institut Pasteur, April, 1900. A translation of the article by Danyz 
appeared in the Public Health Repokt.s of May 25, 1900, Vol. XV, No. 21. 
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