THE BACILLUS OF BUBONIC PLAGUE. 271 



that modem methods of investigation have shed upon 

 the etiol(^y 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 

 epidemics and pandemics of plague have made their 

 appearance in Europe at different times. During and 

 after the Middle Ages it was more or less frequent in 

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

 Grermany, and Great Britain. In history it is vari- 

 ously known as the ''Justinian Plague" of the sixth 

 century, the ''Black Death" of the fourteenth cen- 

 tury, and the " Great Plague of London" of the sev- 

 enteenth century, though it is difficult to say to what 

 extent these pestilences were uncomplicated manifesta- 

 tions of genuine bubonic plague. During the existence 

 of the Justinian Plague 10,000 people are said to have 

 died in Constantinople in a single day, and Hecker esti- 

 mates 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 of London (1664-'65) the total mortality for one 

 year was 68,596, out of an estimated population of 

 460,000 souls. 



It is not surprising to learn that it was to guard 

 against the plague that quarantine regulations were 

 first established. 



For the most recent, and probably the most exact 

 information concerning the cause and pathology of the 

 plague we are indebted to the investigations of Yersin, 



