18 CIRCULAR 4 2 3, U. S. DEPARTMENT OF AGRICULTURE 



calcium cyanide is highly effective in gassing rats in their burrows 

 and other enclosed places, including such partially open ones as 

 corncribs. Killing a few rats is only a temporary expediency, how- 

 ever, and usually should be accompanied by the elimination of rat 

 harborage and the rat proofing of buildings. Any one of a number 

 of poisons can be successfully used, but bait prepared with red squill 

 is primarily to be recommended, not only because it kills the rats but 

 because it is relatively harmless to humans and domestic animals. 

 Detailed instructions for preparing and distributing red-squill baits 

 and for gassing, trapping, and otherwise controlling rats are given 

 in Farmers' Bulletin 1533, Rat Control, and methods of shutting rats 

 out of buildings and premises are described in Farmers' Bulletin 

 1638, Eat Proofing Buildings and Premises. Both publications are 

 available, free of charge, so long as the supply lasts, on application 

 to the Office of Information, United States Department of Agricul- 

 ture, Washington, D. C. 



