148 



Very little can be said of the relation of mice ( M. musculus) to the 

 epidemic. While many thousands were trapped, only a few hundred 

 were examined microscopically and in these no infection was found. 

 They are nonmigratory in habit and for this reason are not considered 

 of much importance from an epizoological standpoint. 



Transmission from man to man was observed in but a small per- 

 centage of cases, 3 per cent to be exact. In these the probability 

 of transference by fleas (P. irritans) or by bugs (Oimex) must, be ad- 

 mitted. When more than one case occurred in a house a common 

 soiurce of infection was indicated, such cases occurring simultane- 

 ously or within from forty-eight to seventy-two hours after the first. 

 Deratization was the measure mainly relied upon. After an infected 

 house was rat-proofed, and the harboring places in the block de- 

 stroyed, no further cases occurred. 



The course of epizootic plague was not interrupted an any time 

 by climatic conditions, there being as many cases in proportion to 

 the rat population in the winter of 1908 as there were at the height 

 of the epidemic. The last case of human plague occurred January 

 30, 1908, but the infection remained active among rats for eight 

 months longer, or until October 21, 1908. (See following table.) 



Month. 



September . 



October. 



November . 



December. . 



1908. 



January.. 



February. 



March. 



April . 



May. 



