CHAPTER XLI 



PLAGUE AND BACILLUS PESTIS 

 (The So-called HaemorrJiagic Septicaemia Group] 



Plague. The history of epidemic diseases has no more terrifying 

 chapter than that of plague. 1 Sweeping, time and again, over large 

 areas of the civilized world, its scope and mortality were often so 

 great that all forms of human activity were temporarily paralyzed. 

 In the reign of Justinian almost fifty per cent of the entire popula- 

 tion of the Roman Empire perished from the disease. The " Black 

 Death" which swept over Europe during the fourteenth century 

 killed about twenty-five million people. Smaller epidemics, appear- 

 ing in numerous parts of the world during the sixteenth, seventeenth, 

 and eighteenth centuries, have claimed innumerable victims. In 

 1893 plague appeared in Hong Kong. During the epidemic which 

 followed, Bacillus pestis, now recognized as the etiological factor 

 of the disease, was discovered by Kitasato 2 and by Yersin, 8 inde- 

 pendently of each other. By both observers the bacillus could 

 invariably be found in the pus from the bubos of afflicted persons. 

 It could be demonstrated in enormous numbers in the cadavers of 

 victims. The constancy of the occurrence of the bacillus in patients, 

 shown in the innumerable researches of many bacteriologists, would 

 alone be sufficient evidence of its etiological relationship to the 

 disease. This evidence was strengthened, moreover, by accidental 

 infections which occurred in Vienna in 1898, with laboratory 

 cultures. 



Since that time the investigations of plague cases and plague 

 outbreaks by individual bacteriologists and by commissions of many 

 governments have established the relationship between the disease 

 and the bacillus to such a degree that there is not the shadow of 

 a doubt as to its etiological significance. 



TTaiulb. <1. liistor.-ooj?r. Path.," 1881. 

 *Kitaxato, Lancet, 1894. 

 9 Yersin, Ann. dc 1'inst. Pasteur, 1894. 



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