BACILLUS PESTIS 121 



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 dis- 

 ease 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 in- 

 fected, 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 foot* 

 hold. The incubation is three to seven days. The bacteria 

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

 numbers. They may be also in dejecta. Many suppose 

 them to be in the breath, but this is probably erroneous. 

 They are in the droplets of saliva expelled by coughing, 

 sneezing, and talking. It is customary in times of epidemics 

 to go about with a towel over the nose and mouth, with the 

 feet and ankles well bound, and all surfaces covered. Sputum, 

 urine, and feces should be received into 5 per cent, carbolic 

 acid and allowed to remain, well mixed, for tw r o hours. Dress- 

 ings from ulcerated surfaces must be burned. Doors and 

 windows must be screened against flies and mosquitoes. 

 The room must be rat- and mouse-free. After death formal- 



