272 



BACTERIOLOGY. 



of Kitasato, and of Aoyama, conducted during the epi- 

 demic of 1894 in Hong-Kong, China. The results of 

 these studies indicate that bubonic plague is an infec- 

 tious, not markedly contagious, disease that depends for 

 its existence upon the presence in the tissues of a spe- 

 cific micro-organism — the so-called plague or pest 

 bacillus. 



Fig. 60. 

 A 



^oA^y^ 



Bacillus of bubonic plague: A, in pus from suppurating bubo ; B, the 

 bacilli very much enlarged to show peculiar polar staining. 



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 centre. It is some- 

 times capsulated; is non-spore-forming; is aerobic, and 



