POISONS OF VEGETABLE OBIGIN 219 



suspension of the dried powdered crude root of D* 

 eiliptica. A solution of 1 in 10,000 killed the larvae in 

 twenty-nine hours and the pupas in twenty-four hours 

 to tlu'ee or four days. Another experiment with the 

 larv® of Culex pipiens showed that they died in less than 

 sixteen hours (pupae in less than twenty-four hours) 

 with solutions of 1 in 1,000, 1 m 2,000 and 1 in 5,000 of 

 the whole root ; with 1 in 10,000 the larvae were killed 

 in twenty houi's and the pupae in twenty-four hours. 

 A solution of 1 in 1,000 of the extract is enough to make 

 the w^ater cloudy. Durham notes that the di'ug dried 

 in Malaya loses much moisture when air-dried in this 

 country : using wetter or fresh root undried would 

 make the effective proportion of the root to water much 

 higher ; at the same time crushing the root up with 

 water is likely to extract more of the juice when not so 

 dry. 



Cultivation of D. elhptica on a large scale with the 

 object of making an insecticide has already been 

 established ; there seems no reason why it should not 

 become a profitable addition to the industries of Malaya. 

 This valuable property of tuba might well prove to be 

 a practical asset in malaria and filaria compaigns 

 if directed against mosquito larvte ; but it must be 

 remembered that fish will also succumb. The pos- 

 sibihty of a purified preparation being valuable as 

 a therapeutic agent was mooted many years ago : 

 during the war the writer suggested that as a drug the 

 active principle might prove to be a definite poison to 

 the protozoa causing malaria ; but it was considered 

 inadvisable to experiment with it clinically without 

 previous standardisation. 



The Chemistry of Derrid. — The active principle 

 of tuba (Derris eiliptica) j described by Greshoff in 1890, 

 and named by him " derrid/' is a nitrogen-free, non- 



