BUBONIC PLAGUE. 293 



The plague bacillus does not form indol, nor does it fer- 

 ment. A slight amount of acid is formed. 



Vitality : A temperature of 55 C. kills the germ in ten 

 minutes ; 1 : 1000 bichloride kills immediately ; and 1 per 

 cent, carbolic acid or lysol solution in ten minutes. Weak 

 solutions of the mineral acids are rapidly destructive. The 

 bacillus does not resist drying, nor does it survive transplan- 

 tation to either sterilized or non-sterilized water for any length 

 of time. 



Pathogenesis : The plague bacillus is pathogenic for man 

 and for animals, especially the rodent, which is the usual cause 



FIG. 131. 



Bacillus of bubonic plague. (Yersin.) 



of widespread epidemics of plague. The rat acquires the dis- 

 ease by eating plague-infected food or the bodies of animals 

 dead of plague. When the animal sickens, it usually seeks 

 refuge in some dark place, like the cellar of a house or the 

 hold of a ship, where it dies. In this way infection is carried 

 from place to place and over great distances in an incredibly 

 short time. Such houses and ships become known as plague- 

 houses or plague-ships; and the disease may remain limited 

 to its boundaries unless the persons infected with the disease 

 are carried to other places. 



