4 LEAFLET 6 5, U. S, DEPARTMENT OF AGRICULTURE 



ditions killed 14-pound rats, in doses varying from less than half a 

 grain of squill to more than 35 grains. Sun-dried squill powders, 

 which can be produced inexpensively, are considered unreliable, as 

 they vary from a fairly high toxicity to practically none. White- 

 squill powders have failed to kill in doses up to TO grains and are 

 therefore apparently nontoxic to rats. 



The department's investigations of numerous manufacturing pro- 

 cesses have demonstrated that it is necessary to dry red squill under 

 controlled temperature conditions in order to obtain 

 Preparation a powder of maximum toxicity. The bulbs are sliced 

 of Red-Squill thin after the dry outer husks have been removed and 

 Powders then are placed in a previously heated drying oven 



and held at a constant heat of 80° C. (176°* F.) until 

 thoroughly dried. (Red squill dried at higher or lower temperatures 

 has been found less toxic than when dried at approximately 80° C.) 

 After being dried the squill should be ground fine enough to pass 

 through a 40-mesh sieve, when it should be packed in air-tight con- 

 tainers, as otherwise moisture absorbed from the air will cause the 

 powder to harden. Thoroughly dried, squill apparently does not 

 deteriorate, and kept in an air-tight container it will retain its orig- 

 inal toxicity indefinitely. 



Powders made by this process should kill rats in doses of less than 

 3 grains of squill per pound of body weight. Because of the vari- 

 ability of different lots of red squill, manufacturers should care- 

 fully test the toxicity of every shipment. This may be done by feed- 

 ing carefully weighed quantities of the powders to five or more white 

 rats that have previously been starved for 18 hours. The rats should 

 be weighed and placed in separate cages. The squill to be tested 

 should be mixed thoroughly with fine meal in 10 per cent concentra- 

 tion and fed to the rats in quantities so computed as to give the rats 

 closes of iy 2 , 3, and 5 grains per pound of body weight in order to 

 determine the approximate minimum lethal dose. The minimum 

 lethal dose is the smallest dose that will kill within five days all 

 rats fed. 



This process is somewhat difficult unless the necessary equipment is 

 available. When such equipment is lacking it is advisable to have 

 the tests made by a commercial bioassayer. If all rats do not die 

 from doses of 5 grains of squill per pound of body weight, the powder 

 is too weak for an effective raticide. A very toxic powder should kill 

 all rats at 3 grains per pound and at least 50 per cent with a dose of 

 iy 2 grains per pound. Variation in the toxicity of different lots of 

 squill powder can be overcome by mixing powders of higher toxicity 

 with those of lower so long as the resulting compound will kill all 

 rats when fed at the rate of 5 grains per pound of body weight. This 

 has been suggested as a standard, but oven-dried squill powders now 

 on the market are more toxic. Highly toxic powders may be mixed 

 with food in the proportion of 1 ounce of squill to 1 pound of food, 

 which will insure the rat getting a lethal dose even if it eats only a 

 small quantity of the bait. (It is safe to figure that a rat will eat 

 enough bait at one time to equal 1 per cent of its body weight.) 



