BACILLUS PEST IS 133 



are susceptible to plague, it practically being endemic 

 among them in certain countries, and they contract 

 it from biting the living, feeding on the dead, soiling 

 themselves on dressings or excreta, but principally by 

 their parasitic fleas. 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 bare-foot may be infected. By any of 

 the skin-wound methods, the germs enter the sub- 

 cutaneous tissue, are carried to the nearest lymph 

 glands, where they set up inflammation and pus, which 

 is frequently discharged by rupture through the skin. 

 The bacteria enter the blood stream and produce a 

 septicemia. 



In the pneumonic form the bacteria are inhaled and 

 set up a pneumonia not unlike that produced by 

 ordinary cocci. Here, again, there may be suppuration 

 and septicemia. 



The bacilli produce the characteristic results chiefly 

 by means of their endotoxins, little or no separable 

 poisons being formed. There is no difference in the 

 bacteria or their products in the two forms, these 

 simply depending upon the mode of entry. The 

 mortality of this disease is very high, due to the rapid 

 progress made after the disease gains a foothold. 

 The incubation is three to seven days. The bacteria 

 are present in the blood, pus, and sputum in enormous 



