PLAGUE 243 



Plague. — This disease, sometimes known as black 

 death, has for many centuries been one of the most 

 terrible diseases known to man. Early in the Christian 

 Era it raged for more than fifty years and swept away 

 the people of many districts. Again in the latter part 

 of the Fourteenth Century an outbreak occurred that 

 spread over the entire world, and destroyed, it is esti- 

 mated, 25,000,000 people. In more recent times other 

 epidemics have occurred, and, while of less extent, their 

 effects have nevertheless been frightful. 



During one of these recent outbreaks it was discovered 

 that a minute germ invariably occurs in the bodies 

 of plague-afflicted patients, and it was also proved 

 that this germ when it gains access to the blood of other 

 individuals produces the disease. It has been known 

 for centuries that when there is an outbreak of plague 

 there is also a high death rate among rats. These animals 

 might therefore in some way be responsible for the 

 disease, but in what way was discovered less than twenty 

 years ago. 



Fleas and Plague. — It is now known that dogs, cats, 

 mice, and especially rats, are subject to the attacks of 

 plague, and furthermore it has been shown that when 

 such animals die of the disease the fleas which infest 

 their bodies leave and seek new hosts. The new victims 

 may be almost any of the warm-blooded animals, and 

 when attacked by the flea they develop the disease owing 

 to germs introduced into the body. This same insect may 

 escape and inoculate new hosts, or the same patient may 

 be bitten by other fleas, which then transmit the disease 

 to other animals. And thus the disease spreads, due in 

 every instance to the activity of this one type of insect. 



These results are now definitely established, and have 

 led to the introduction of international sanitary measures 

 which have for their goal (1) the destruction of rats 

 and other flea-carrying animals in plague-infested dis- 

 tricts, and (2) the isolation of stricken human beings. 



