30 ANIMAL COMPETITORS 
resting on the concrete is just as satisfactory so far 
as the exclusion of rats is concerned.”’ 
Keeping food from rats. The general rat- 
proofing of buildings is the most important step 
in limiting the food supply of rats. The effect 
of an abundance of food on the breeding of 
rodents has already been mentioned. Well-fed 
rats mature quickly, breed often, and have large 
litters of young. Besides limiting reproduc- 
tion, scarcity of food will make the measures 
to destroy the animals by traps, ‘poisons, or 
bacterial cultures far more effective. But 
since much of the animals’ food consists of 
garbage and other waste materials, offal of any 
kind must be so disposed of that rats can not 
obtain it. The best method is by burning it. 
The management of slaughter-houses in the 
country,‘in particular, needs reform. It is a 
common practice to leave offal of slaughtered 
animals to be eaten by both rats and swine. 
Such places are not only centers of rat-propaga- 
tion, but are the chief means of perpetuating 
trichine in pork. All this should be changed in 
fact and by law. The offal should be promptly 
cremated or otherwise disposed of. There is 
