16 



farmers' bulletin 896. 



Among the principal poisons that have been recommended for 

 killing rats and mice are barimn carbonate, strychnin, arsenic, phos- 

 phorus, and squills. 



Barium carbonate. — One of the cheapest and most effective poisons 

 for rats and mice is barium carbonate. This mineral has the advan- 

 tage of being without taste or smell. It has a corrosive action on the 

 mucous lining of the stomach and is dangerous to larger animals if 

 taken in sufficient quantity. In the small doses fed to rats and mice 

 it would be harmless to domestic animals. Its action upon rats is 

 slow, and. if exit is possible the animals usually leave the premises in 

 search of w^ater. For this reason the poison may frequently, though 

 not always, be used in houses without disagreeable consequences. 



Barium carbonate may be fed in the form of dough composed of 

 four parts of meal or flour and one part of the mineral. A more 

 convenient bait is ordinary oatmeal with about one-eighth of its bulk 

 of the mineral, mixed with water into a stiff dough. A third plan is 

 to spread the barium carbonate upon fish, toasted bread (moistened), 

 or ordinary bread and butter. The prepared bait should be placed in 

 rat runs, about a teaspoonful at a place. If a single application of 

 the poison fails to kill or drive away all rats from the premises, it 

 should be repeated with a change of bait. 



Strychnin. — Strychnin is too rapid in action to make its use for 

 rats desirable in houses, but elsewhere it may be employed effectively. 

 Strychnia sulphate is the best form to use. The dry crystals may be 

 inserted in small pieces of raw meat, Vienna sausage, or toasted 

 cheese, and these placed in rat runs or burrows; or oatmeal may be 

 moistened with a strychnin sirup and small quantities laid in the 

 same way. 



Strychnin sirup is prepared as follows: Dissolve a half ounce of 

 strychnia sulphate in a pint of boiling water; add a pint of thick 

 sugar sirup and stir thoroughly. A smaller quantity may be pre- 

 pared with a proportional quantity of water and sirup. In prepar- 

 ing the bait it is necessary to moisten all the oatmeal with the sirup. 

 Wheat and corn are excellent alternative baits. The grain should 

 be soaked overnight in the strychnin sirup. 



Arsenic. — Arsenic is probably the most popular of the rat poisons, 

 owing to its cheapness, yet our experiments prove that, measured 

 by the results obtained, arsenic is dearer than strychnin. Besides, 

 arsenic is extremely variable in its effect upon rats, and if the ani- 

 mals survive a first dose it is very difficult to induce them to take 

 another. 



Powdered white arsenic (arsenious acid) may be fed to rats in 

 almost any of the baits mentioned under barium carbonate and 

 strychnin. It has been used successfully when rubbed into fresh 

 fish or spread on buttered toast. Another method is to mix twelve 



