392 APPLICATION OF METHODS OF BACTERIOLOGY 



teenth century, though it is difficult to say to what extent 

 these outbreaks were uncomplicated manifestations of 

 genuine bubonic plague. During the existence of the Jus- 

 tinian 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 of London (1664-65) 

 the total mortality for one year was 68,596, out of an esti- 

 mated population of 460,000 souls. 



It is not surprising to learn that it was to guard against 

 the plague that quarantine regulations were first estab- 

 lished. 



The first and certainly the most exact information con- 

 cerning the exciting cause and the pathology of the plague 

 was furnished by investigations of Yersin, of Kitasato, and 

 of Aoyama, conducted during the epidemic of 1894 in Hong 

 Kong, China; although since then numerous other inves- 

 tigators have made additional important contributions to 

 our knowledge of the subject. The results of these studies 

 demonstrate that bubonic plague is an infectious, not 

 markedly contagious disease (except in the case of the 

 pulmonic variety), that depends for its existence upon the 

 presence in the tissues of a specific microorganism the 

 so-called plague or pest bacillus. 



This organism is described as a short, oval bacillus, usually 

 seen single, sometimes joined end to end in pairs or threes, 

 less commonly as longer threads. It stains more readily 

 at its ends than at its center. It is sometimes capsulated; 

 is non-spore-forming; is aerobic, and is non-motile. It is 

 found in large numbers in suppurating glands. (Fig. 73.) 

 It is also to be detected in the blood, spleen, lungs, liver, 



