306 BACTERIA 



Plague. This disease, like anthrax and leprosy, has a 

 long historical record behind it. As the Black Death it 

 decimated the population of England in the fourteenth 

 century, and visited the country again in epidemic form in 

 the middle of the seventeenth century, when it was called 

 the Great Plague. Now, it is highly probable that these two 

 scourges and the recent epidemic in the East are all forms 

 of one and the same disease. As a matter of fact, it is 

 difficult to be sure what was the exact pathology of a num- 

 ber of the grievous ailments which troubled our country in 

 the Middle Ages, but from all accounts bubonic plague and 

 true leprosy were amongst them. The former came and 



7'" 



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BACILLUS OF PLAGUE 



went spasmodically, as is its habit; the latter dragged 

 through the length of several centuries. 



The distribution of plague at the present time is fort- 

 unately a somewhat limited one, namely, a definite area in 

 Asia known as the " Plague Belt." From Mesopotamia, 

 as a sort of focus, the disease spreads northwards to the 

 Caspian Sea, westwards to the Red Sea, southwards as far 

 as Central India, and eastwards as far as the China Sea. 

 This constitutes the " belt," but the disease may take an 

 epidemic form, and is readily, though very slowly, conveyed 

 by infection or contagion. It appears to be infectious by 

 means of infective dust, and contagious by prolonged and 

 intimate contact with the plague-stricken. Rats have been 

 accused of conveying the disease from port to port, and 



