294 ANIMAL COMPETITORS 



arsenic is required to kill. Actual field experi- 

 ments show that an ounce of strychnine, if 

 properly distributed, is enough to kill 4,500 

 prairie-dogs or large ground-squirrels, or 9,000 

 field-mice. 



Various other poisons, both mineral and 

 vegetable, have been used, but none is to be 

 recommended as compared with strychnine, 

 with the possible exception of barium carbonate 

 as an agent for killing rats and mice about 

 buildings. This mineral, which is cheap, has 

 the advantage of being without taste or smell, 

 and also that in the small doses fed to rats 

 and mice it would be harmless to domestic ani- 

 mals. Its action upon rats is slow, and if exit 

 is possible, they usually leave the premises in 

 search of water. 



Poisoning rats and house-mice. For the 

 reasons above given phosphorus and arsenic 

 are not recommended in poisoning rats and 

 mice; although powdered white arsenic mixed 

 with oatmeal and sugar, or made into a paste 

 of 12 parts of cornmeal and one part of arsenic 

 with whites of eggs, is often effective. 



Barium carbonate may be fed in the form of 



