INSECTS AND DISEASE 
cities where plague infection is likely to enter, comprehensive cam- 
paigns must be organized for the removal of breeding and harborage 
places of rats by cleaning up rubbish, for the starving out of rats by 
covering garbage and eliminating other accumulations of food, for 
trapping and shooting and poisoning rats, and for excluding rats 
from buildings by various forms of ratproof construction. The 
natural enemies of the rat,—cats, dogs, and ferrets, skunks, foxes, 
coyotes, weasels, minks, hawks, owls, snakes, and _ alligators—are 
often of great assistance in this campaign. 

Fig. 31. THE SECOND PANDEMIC OF PLAGUE. 
EXTENSION OF THE DISEASE BETWEEN 1200 AND 1450 A. D. 
These methods of rat suppression have been widely successful 
in their application to the control of bubonic plague. The early 
history of the present pandemic of plague is precisely like that of 
the one which began in the eleventh century. It started in China, 
spread to Manchuria in one direction, and killed its six millions 
in India. Thence, following the trade routes as of old, plague 
infection has been carried to seaports all over the world. It has 
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