122 THE ACUTE SELF-LIMITED INFECTIONS 



BACILLUS PESTIS 



Bubonic plague or "the plague" or "pest" is an acute 

 infectious disease characterized by high fever, swell- 

 ings of the regional lymph glands, or pneumonia, with 

 occasional hemorrhages (black death) under the skin 

 in severe cases, caused by the Bacillus pestis. The 

 disease is fostered by unhygienic conditions, and may 

 be said to be more common in those countries where 

 the people go about scantily clothed, especially about 

 the feet. There are two forms of the plague, according 

 to the place of entrance of the bacteria. The bubonic 

 type is that in which painful swellings and abscesses 

 occur in lymph glands when germs enter through the 

 skin and the pneumonic type occurs when they are 

 inhaled. 



The bacteria enter chiefly through the skin by way 

 of minute wounds, or as was shown in India, by the bite 

 of a rat flea, parasitic to man in that country. Rats and 

 mice, indeed all rodents, are susceptible to plague and 

 they contract it from biting the living, feeding on the 

 dead and soiling themselves on dressings or excreta. 

 When infected they have great numbers of bacilli in 

 their blood, thus easily passing them on to fleas that bite 

 them. The fleas then pass the disease to other rats 

 and to man. Furthermore, rats may vomit, defecate, 

 and die where they can infect objects later handled 

 by persons. The rats are said to transmit the disease 

 also by biting people. In epidemic times the ground 

 becomes infected, and persons going barefoot may be 

 infected. By any of the skin wound methods, the 

 germs enter the subcutaneous tissue, are carried to 



