19-21.] 



Research (Rat) TjAhoratory. 



717 



Apart from mere palatability, several points require considera- 

 tion, such as the size of the bait and the amount of poison in it. 

 A bait should be small enough for a hungry rat to eat it all, and 

 should contain enough poison to kill. If a bait will kill even 

 if only half of it is eaten, so much the better. 



Experiments carried out at the Laboratory showed that rats 

 eat about one-tenth of their body weight per diem; hence a bait 

 of 30 to 60 grains is suitable and represents about one-tenth of a 

 day's food supply. Each such bait should contain a lethal dose ; 

 to obtain this the following percentages of toxic agent in the 

 baits prepared are used: — 



Arsenic 5% Each bait being about 20 grains. 



Barium Carbonate 25% ,, ,, 30 ,, 



Squill Bulbs 20% 50 

 Squill Powder 20% 25 



Baits should be prepared in such a way that they are ready 

 for use; such operations as spreading on bread, etc., should be 

 avoided. The quantity to be used should be clearly stated in 

 common measures, such as a teaspoonful. It is, however, an 

 advantage to prepare the bait in tablet or biscuit form, as the 

 quantity used and the amount of poison per bait are then easily 

 controlled. The most important point of all is that the bait should 

 be attractive to the rodents, and this can only be decided by 

 experiment and observation in the I^aboratory followed by field 

 trials. It is here that the close association of the Factory and 

 Laboratory is specially valuable. 



Each poison should be made up in several varieties of bait, 

 so that if one kind is not taken a change can bo made. The 

 Tuost frequently used bait is a mixture of oatmeal and fat, to 

 form a hard paste ; this is more useful in winter than in summer. 

 Another very useful way is to mix the poison with flour, work 

 up into a dough, and prepare biscuits or tablets, which are then 

 baked. Variety of flavour can be obtained by introducing -such 

 substances as grated cheese (the older the better), minced fish 

 or fish meal, and sugar. Baits with no natural odour are slightly 

 flavoured with aniseed or rhodium oil. Differences of opinion 

 exist as to the advantages of this but slight flavourings are 

 generally favoured. 



Successful rat destruction depends not only on the choice of 

 suitable toxic agents, made with due regard to their chemical and 

 toxic properties, but also on the adaptability of the baits to the 

 varying tastes of the rat. In England, the rat generally prefers 

 variety, i.e., in a cheesemonger's the best bait would probably 



