716 



Ee SEARCH (Rat) Laboratory. 



[Nov., 



be poisonous to rats. Work has also been done on possible 

 alternative poisons to those in present use, so far, however, 

 with inconclusive results. 



Other Poisons. — It has akeady been indicated that the choice 

 of a poison is very wide; the poisons actually in use, however, 

 are comparatively few. It may be well to summarise the 

 requirements of a practical rat poison. It must be : — 



1. Eelatively harmless to domestic animals. 



2. Cheap and readily procurable. 



3. Effective on rats and mice, that is, reasonably small doses 

 should kill. 



4. Tasteless, or, at any rate, without a repellant taste. 



5. FJasy and clean to handle and be readily incorporated for 

 making the bait. 



6. Capable of keeping well and retaining its toxicity. 

 These conditions narrow down the choice considerably, and 



there are not a great many substances which will satisfy them. 

 The first condition practically eliminates all the substances 

 popularly recognised as poisons; nevertheless a great many of 

 the rat poisons on the market contain either arsenic, strychnine, 

 or phosphorus, the last-named being especially popular, partly 

 l-ecause it can be bought without the restrictions of the Pharmacy 

 Act, which apply to the first two. Where there is little or na 

 risk of poisoning other animals, the use of these poisons is safe 

 enough, and they are certainly effective, though arsenic is 

 somewhat variable in its results, while the use of phosphorus is 

 attended by some risk of fire. Actually, strychnine is said to be 

 cheapest, per rat killed. As a general rule, however, the indis- 

 criminate use of these dangerous poisons is to be deprecated, 

 and the use of alternative and less dangerous poisons should be 

 encouraged. 



Of the less dangerous poisons Barium Carbonate and Eed 

 Squill have been found most effective for killing rats. In fact, 

 they are just as good and cheap as the more dangerous poisons, 

 and they have the great advantage of being far less poisonous 

 to domestic animals and human beings. 



The Composition of Baits. — There is, of course, no such thing 

 as a poison which will kill rats and mice and nothing else : what 

 is wanted is to reduce the risk as much as possible by using 

 poisons to which rats and mice are peculiarly susceptible. Now^ 

 the success of a rat poison depends not so much on its actual 

 toxicity as on its beiag presented in a form that is acceptable tO' 

 and readily taken by the rodents. 



