i8o Journal of Agricultural Research voi. xvii, no. s 



tadpoles, toads, and monkeys. The following are the salient conclu- 

 sions of his investigation: (i) Boiling does not destroy the toxic action 

 of the sap ; (2) roots kept three months in a cupboard retain their strength ; 



(3) milky extract introduced into a fish's stomach is rapidly fatal; 



(4) tadpoles are fatally affected, but stronger extracts are required to 

 kill them than to kill fish ; (5) much stronger doses are required to kill 

 mosquito larvae than to kill either fish or tadpoles; (6) the extract from 

 1/50 gm.of the roots when injected subcutaneously is fatal to toads, and 

 the extract from i /i 2 gm. causes death when introduced into the stomach ; 

 and (7) when the extract from 2 gm. of the roots is injected subcuta- 

 neously or introduced into a monkey's stomach death results. Campbell 

 further states (p. 134-135) '■ 



From the results on different animals it is evident that the poison affects the more 

 highly developed members of the animal kingdom more readily than it does the 

 primitive members. This is only to be expected since its action concerns the 

 brain and one particular part of this, namely, the medulla oblongata. 



It could be used to destroy mosquito larva:, but it should be used in solutions not 

 weaker than i in 1,000, that is just enough of the extract should be added to the pool 

 to make the water cloudy. 



METHODS OF PREPARING AND TESTING EXTRACTS FROM DERRIS 



MATERIALS 



The many preliminary experiments performed indicate that Derris 

 (probably D. elliptica) is promising as a contact insecticide and as a 

 stomach poison but is of no practical use as a fumigant. The best 

 methods of applying it — whether in the form of powder, suspended in 

 water or in the form of extract mixed with water or with soap solu- 

 tion — now remain to be determined. 



A vegetable insecticide is usually applied either in the form of fine 

 powder or as a spray mixture. This mixture may consist of any one 

 of the following four combinations: (i) Powder suspended in water; (2) 

 aqueous extract of the material diluted with Avater; (3) a solution con- 

 sisting of water and a small amount of a concentrated form of the active 

 constituent; and (4) a small quantity of a concentrated form of the 

 active principle suspended in water. 



Since Derris material must be imported, only dried roots and stems 

 may be secured for insecticidal purposes. As already stated under the 

 historical review, the natives pound the roots of Derris into a pulp 

 which they then throw into the water inhabited by fish. This allows the 

 juices of the plant to mix freely with the water and is the simplest way 

 of obtaining a water extract, but will water remove the toxic principle 

 after the roots have become dry ? The chief object of the investigation 

 discussed under the preceding heading was to make a study of the 

 different methods of extracting Derris and to determine the value of 

 various solvents in order that a simple and economical method might 

 be devised for obtaining the active principle and applying the extracts. 



