176 BUBONIC PLAGUE. 



At what temperature does it grow ? 

 In what artificial media does it grow ? 

 What must be added to this media to facilitate its growth ? 

 What is the appearance of the colonies, in glycerin ? On agar ? In blood- 

 serum ? 



How does it grow in bouillon ? 



What is the resisting power of this bacillus ? 



What animals are susceptible ? 



Where is the bacillus found in animals? 



What is peculiar about the retention of this bacillus by some persons? 



How may this explain the spread of the disease ? 



CHAPTER XX. 

 BUBONIC PLAGUE. 



Bacillus Pestis. 



History. Under various names and from the remotest 

 times epidemics of bubonic plague have appeared in the old 

 world, causing an immense fatality. 



Yersin and Kitasato, in 1894, working independently, have 

 both discovered the pathogenic germ of this disease in the 

 suppurating buboes, blood, internal organs, and excretions of 

 persons affected, and called it the Bacillus pestis. 



Morphology. This bacillus is a short, oval, thick rod, 

 occurring singly or in pairs, or sometimes by the union of a 

 number forming long filaments or threads. Staining with 

 all the anilin dyes, but not by Gram's method. In stained 

 preparations the centre of the bacilli cell stains less well 

 than the ends of the rod, giving it quite a characteristic 

 appearance. (Plate V.) 



This bacillus has no flagella. 



Biologic Characters. The Bacillus pestis is a non-motile 

 aerobic. It grows at all temperatures, but best between 36 

 and 39 C. It is killed by a temperature of 80 C. after an 

 exposure of a half-hour, and in five minutes by an exposure 

 to 100 C. in the steam sterilizer. It grows in all the arti- 



