11 



spreading jolague from rats to men are the rat fleas. In taking 

 up this question with reference to local conditions, it was found 

 that these rodents in Manila are infested by a species of sipho- 

 naptera not heretofore described. It, however, appears that this 

 new species of flea has not taken any part in the conveyance of 

 the disease, which may or may not have been first imported to 

 this city through the agency of rats. 



It is a source of great satisfaction to the writer to be in a 

 position to present this paper well illustrated with colored plates, 

 photographs, and microphoto graphs, by which whatever value it pos- 

 sesses, both as a scientific contribution and as a guide in the post- 

 mortem diagnosis of plague, is undoubtedly greatly enhanced. 



For a revision of the manuscript the author is indebted to Drs. 

 Paul C. Freer and Eichard P. Strong. The colored drawings 

 were prepared by Mr. T. Espinosa and Mr. W. Schultze and most 

 of the microphotogra|)hs by Mr. Chas. Martin, all members of our 

 laboratory staff. 



THE DISCOVERY OF THE PLAGUE BACILLUS. 



The etiologic factor of plague in all of its various forms is 

 a specific micro-organism — the j^lague bacillus. It can generally, 

 without difficulty, be cultivated in pure culture from cases of 

 plague in man. In susceptible animals it produces a disease 

 identical with or similar to that found in the human race, and in 

 some deplorable laboratory accidents, in locations where no plague 

 existed, it has caused typical fatal pest infection in men. The 

 names both of Yersin and of Kitasato are connected witli the 

 discovery of the plague bacillus during the epidemic in Hongkong 

 in 1894. To the claims of each of these investigators to be the 

 independent discoverer of the plague germ one may well apply 

 the words of the German poet, that it is "Von den Parteien Hass 

 und Gunst entstellt." 



Some writers upon plague dispute Yersin's claim; while not 

 a few, and particularly his own countrymen, maintain that Kita- 

 sato is not entitled to any fame in connection with the original 

 finding of Bacillus pestis. Ogata, for instance, tersely states: 



Many aiitiiors believe that tlie plague bacillus of Kitasato and that of 

 Yersin are identical, but svich is not tlie case. They are two absolutely 

 different kinds of bacilli. 



