Sept. 3, 1917 Quassia Extract as a Contact Insecticide 527 



(2) Quassia chips boiled longer than four hours in water yield but 

 little more extract than those boiled for just four hours, and the quantity 

 obtained is about 1.5 times that obtained from chips soaked in water for 

 24 hours. Extracts from chips soaked in water are usually less effective 

 than those from chips boiled in water, but not one of those tested would 

 be efficient in practical work. 



(3) The smaller the quassia chips and the finer the quassia powder used, 

 the greater is the quantity of extract removed. 



(4) The larger the volume of water used as a solvent, the greater is the 

 quantity of extract removed; for example, 10 gms. of chips soaked for 

 24 hours in 3,000 c. c. of water yield 32.1 per cent more extract than 10 

 gms. soaked for the same period in 250 c. c. of water. The practical ex- 

 periments well support this view. 



(5) The solubility in water of the quassiin powder used in these experi- 

 ments was found to be i to 3,000. In a 0.05 per cent sodium-carbonate 

 solution, a soap solution (1.8 gm. of soap to 1,000 c. c. of water), and in 

 a 0.05 per cent lye solution its solubility was, respectively, 3, 4, and 5 

 times as great. 



The experimental results obtained with quassiin powder and quassia 

 chips supported this view in only a general way. The sodium-carbonate 

 solution extract w^as only slightly more effective than the water extract. 

 The soap-solution extract and lye-solution extract were equally effective 

 in the laboratory when applied as prepared; but when the former solu- 

 tion was diluted with soap solution and the latter solution with water, 

 the dilutions containing the soap-solution extract were much more 

 effective and also more economical, provided the soap was also added to 

 the dilutions containing the lye-solution extract. Extracts from chips 

 soaked in the solvents mentioned are more effective than those from chips 

 boiled in these solvents. This seems to indicate that at a high tempera- 

 ture alkalies decompose quassiin, or render it insoluble. 



The following results deal with the pharmacological effects of quassiin : 



(i ) A moderately bitter and practically ineffective extract was dissolved 

 from commercially pure quassiin powder, leaving a residue whose water 

 extract was intensely bitter and quite eft'ective. The first extract corre- 

 sponds to quassol, a supposedly inert and tasteless substance with a 

 slight admixture of quassiin; the second extract corresponds exactly to 

 pure quassiin. 



(2) The exhalations alone from the quassiin powder killed aphids, but the 

 exhalations from quassia chips, quassia powder, and those from solutions 

 containing quassiin extract and quassia extract were ineffective. Quassia 

 powder dusted upon insects is ineffective, while quassiin powder is 

 quite effective, indicating that the exhalations pass into the respiratory 

 system and that they then affect the nervous system. The minutest 

 particles of either powder are sufficiently small to pass into the spiracles, 

 but they do not cause death by closing the entrances of the tracheae. 



