CHAPTER XXXII. 



THE BACILLUS OF BUBONIC PLAGUE THE BACILLUS ICTEROIDES 

 THE MICROCOCCUS MELITENSIS. 



Bacillus of Bubonic Plague (Bacillus Bacterium Pestis Bubonicse). 



HISTORICALLY we can trace the bubonic plague back to the third 

 century. In Justinian's reign a great epidemic spread over the Roman 

 empire and before it terminated destroyed in many portions of the 

 country nearly 50 per cent, of the people. Among the most fatal forms 

 of infection is that of the lungs. Pneumonic cases are not alone very 

 serious, but they readily spread infection. The bacillus exciting the 

 disease was discovered simultaneously by Kitasato and Yersin (1894) 

 during an epidemic of the bubonic plague in China. It is found in 

 large numbers in the seropurulent fluid from the recent buboes char- 



FIG. 127 Fio. 128 



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Bacilli froto agar culture. X 1100 diam. Bacilli from bouillon culture. X 1100 diam. 



icteristic of this disease and in the lymphatic glands ; more rarely in 

 ihe internal organs and in the blood, in which it occurs in acute hemor- 

 rhagic cases and shortly before death. It also occurs in malignant 

 cases in the feces of men and animals. The bacillus is closely allied 

 to the hemorrhagic septicaemia group. 



Morphology. The bacilli in smears from acute abscesses or infected 

 tissues are, as a rule, short, thick rods with rounded ends. The central 

 portion of the bacillus is slightly convex. When lightly stained the 

 two ends are more colored than the middle portion. The bacilli are 

 mostly single or in pairs. Bacilli in short chains occur at times. The 



