310 BACTERIOLOGY. 



been described; but when cultivated side by side their 

 biological differences are seen to be so slight as to ren- 

 der it probable that they are but modifications of one 

 and the same species. 



BACILLUS PESTIS, YERSIN, 1894. 

 THE BACILLUS OF BUBONIC PLAGUE. 



Before passing from the subject of suppuration it 

 may not be inappropriate to call attention to the light 

 that modern methods of investigation have shed upon 

 the etiology of bubonic plague, an epidemic disease 

 characterized by suppuration of the lymphatic glands, 

 and accompanied by a very high rate of mortality. 



This pestilence, probably endemic in certain sections 

 of the Orient, is one of the most conspicuous epidemic 

 diseases of history. Since early in the Christian era epi- 

 demics and pandemics of plague have made their appear- 

 ance in Europe at different times. During and for a time 

 after the Middle Ages it was more or less frequent in 

 India, China, Arabia, Northern Africa, Italy, France, 

 Germany, and Great Britain. In history it is variously 

 known as the " Justinian Plague " of the sixth century, 

 the " Black Death " of the fourteenth century, and the 

 " Great Plague of London " of the seventeenth century, 

 though it is difficult to say to what extent these pesti- 

 lences were uncomplicated manifestations of genuine 

 bubonic plague. During the existence of the Justinian 

 Plague 10,000 people are said to have died in Con- 

 stantinople in a single day, and Hecker estimates that 

 during the pandemic of the Black Death 25,000,000 

 people (a quarter of the entire population of Europe) 

 succumbed to the disease. During the Great Plague 



