THE BACILLUS OF BUBONIC PLAGUE. 311 



of London (16 64-' 6 5) 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. 



The first and certainly the most exact information 

 concerning the cause and pathology of the plague re- 

 sulted from the investigations of Yersin, of Kitasato, 

 and of Aoyama, conducted during the epidemic of 1894 

 in Hong-Kong, China; although since then numerous 

 other investigators 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 that 

 depends for its existence upon the presence in the tis- 

 sues of a specific micro-organism 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 centre. It is some- 

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

 is non-motile. It is found in large numbers in suppu- 

 rating glands, and in much smaller numbers in the cir- 

 culating blood. (Fig. 60.) 



It is demonstrable in cover-slip preparations made 

 from the pus and in sections of the glands by the ordi- 

 nary staining-methods. 



Wilm l has found it by culture methods in the spleen, 

 lungs, liver, kidneys, stomach, walls of the intestine, 

 urine, and intestinal contents of fresh cadavers ; and 

 1 Wiliu : Hygieuische Kuudschau, 1897, p. 217. 



