THE PEST OF RATS 19 



Rats as carriers of disease. Finally, rats are 

 always a menace to health, and may become 

 the agents of the dissemination of the most 

 dreadful and virulent of diseases the Asiatic 

 plague, which has more than once decimated 

 the civilized world. It has been calculated that 

 25,000,000 of persons perished in an epidemic 

 of this character which swept over the world 

 in the 14th century; and it did not require the 

 literary genius of a De Foe to perpetuate the 

 memory of the awful visitation which almost 

 depopulated London and set all Europe in 

 mourning toward the end of the IGth century. 

 Even then, in the cloud of mystery, supersti- 

 tion and horror of fear which made most men 

 blind and helpless, the truth was dimly recog- 

 nized by a few, namely that it was not the 

 wrath of God nor the malignancy of some evil 

 spirit nor a miasm from earth or sea that 

 struck men down, but the communication of 

 disease from the sick to the well. This, it was 

 observed, could be effected not only by contact 

 with human victims, but that the contagion was 

 caught and passed on by all the small animals 

 about a house. TTence orders were issued that 



