CHAPTER XXIII. 



PLAGUE. 



BACILLUS PESTIS (YERSIN, KITASATO). 



General Characteristics. A minute, pleomorphous, diplococcoid 

 and elongate, sometimes branched, non-motile, non-flagellated, non- 

 sporogenous, non-chromogenic, aerobic and optionally anaerobic, 

 pathogenic organism, specific for bubonic plague, easily cultivated 

 artificially, and susceptible of staining by ordinary methods, but not 

 by Gram's method. 



Plague, bubonic plague, pest, black plague, " black death," 

 or malignant polyadenitis is an acute epidemic infectious 

 febrile disease of an intensely fatal nature, characterized by 

 inflammatory enlargement and softening of the lymphatic 

 glands, marked pulmonary, cerebral, and vascular disturb- 

 ance, and the presence of the specific bacillus in the lymphatic 

 glands and blood. 



The history of plague is so full of interest that many ref- 

 erences to it appear in popular literature. The student can 

 scarcely find more profitable reading than the "History of the 

 Plague Year in London," by DeFoe, and readers of Boccacio 

 will remember that it was the plague epidemic then raging in 

 Florence that led to the isolation of the group of young 

 people by whom the charming stories of the Decameron were 

 told. 



During the reign of the Emperor Justinian the plague is 

 said to have carried off nearly half of the population of the 

 Roman Empire. In the fourteenth century it is said to have 

 destroyed nearly twenty-five millions of the population of 

 Europe. Epidemics of less severity but attended with great 

 mortality appeared in the sixteenth, seventeenth, and eight- 

 eenth centuries. In 1894 an epidemic broke out in the 

 western Chinese province of Yunnan and reached Canton in 

 January, 1894, thus escaping from its endemic center and 

 began to spread. It can be traced from Canton to Hong- 

 kong. In 1895 it appeared also in Amoy, Macao, and 

 Foochoo. In 1896 it had reached Bombay and reappeared in 

 Hongkong. In 1897 Bombay, the Madras Presidency, the 



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