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keeping rats from their food if their extermination is to be accom- 

 plished. 



With regard to ground squirrels, the use of poisoned wheat very 

 properly enters here. With the changing season ground squirrels 

 change their habitat and food. During early spring these rodents 

 come down from their winter dwellings in the hills and seek burrows 

 in meadow lands and cultivated spots. Months have passed since 

 the squirrel tasted wheat ; his fickle appetite betrays him. From the 

 first spring months until harvest time one can kill thousands of ground 

 squirrels by tempting them with poisoned wheat. But so soon as 

 harvest time comes, they seek new growing green stuffs to eat and 

 thereafter, on through winter, poisoned wheat is ineffective. 



BUILDING THE RAT OUT OF EXISTENCE. 



Most certain of all methods to get rid of rodents is to allow them no 

 place in which to live. San Francisco effects this result through its 

 ordinance, which requires small houses outside certain city limits to 

 be raised so high from the ground that dogs and cats can drive out 

 rats from under them, and which requires all other buildings in the 

 city to be rat proofed with cement or concrete. The latter con- 

 templates foundation walls of concrete or brick sunk at least 1 foot 

 to 18 inches to 2 feet above that surface; the whole ground area 

 inclosed by their foundation walls must be covered with concrete 

 at least 1^ inches in thickness. Thus the entrance of burrowing 

 rodents is prevented. Even where buildings stand upon rock or 

 hardpan, these requirements should be enforced. Rock may crack, 

 gradual weather decay may cause crevices to be found in it unseen 

 crannies may be found by rodents, ajid once the rat lodges in rock 

 his nest is virtually unassailable. With hardpan it is even worse, 

 for the rats can burrow in it, with some difficulty, truly, but when 

 nests are impossible elsewhere, necessity will drive rats to find shelter 

 in hardpan, which will protect them quite as well as rock. In the 

 main, these two points of building rats out of existence, though modi- 

 fied, will apply to any structure. 



Yet any negligence will overthrow these safeguards. The principle 

 is to allow no opening within which rodents may nest. Plank side- 

 walks and back yards will continue the rat nuisance even though 

 buildings are amply protected. Carelessness in throwing old boxes 

 into basements or piling old lumber or refuse within reach will supply 

 shelter for rats despite concreted ground area. The precaution must 

 be constant and consistent. 



Another important phase is to cut off the rodent migrations. 

 Prevent rats from moving from place to place. Their time-honored 

 highway is through sewers. Modern sewers afford no protection, 



