-44- 
The United States Department of Agriculture, Bureau of Entomology 
end Flant Quarantine, Division of Control Investigations ( 294 ) in 1938 
reported that a petroleum ether extract of derris (i. I. No. 2007) 
dissolved in kerosene applied as a srrey to adult houseflies killed 
90 percent after 72 h^urs.. Another petroleum extract af derris 
(I. D. No. 3354) in kerosene killed 86 percent a.-^ter 72 hours. 
Bliss (34) in 1939 published a discussion of the toxicity of insecti 
cides applied jointly. From a study of the dosage-mortality curves f r 
several mixtures containing fixed proportions of the ingredients, pre- 
ferably in comnarison vrith equivalent curves for the isolated active 
ingredients, most cares of combined action can be classified into one 
of the following three types: (l) That in "hich the constituents 
act independently end diversely, so that the toxicity of any combine ti:n 
can be predicted from that of the isoleted components and from the 
association of susceotibilities to the two components. (2) That In 
which the constituents act independently but similarly, so that one 
ingredient can be substituted at a constant ratio for any proportion 
of a second without altering the toxicity of the mixture. Tith homo- 
geneous populations, dosage-mortality curves for the separate ingredients 
and for all mixtures should be parallel. Mixtures in this category 
are more toxic than in the preceding class r-here association may range 
from to 1. (3) Synergism forms the third type of joint action, 
characterized by a toxicity greater than that predicted from studies 
on the isolated constituents. The log LD50 of ether extract for six 
samples of derris root :vas related to the percentage comuosition of 
two components in the extract, rotenone (A) and dehydro mixture (B). 
Since the toxicity of extract could be expressed almost entirely in 
terms of these t^o constituents they r/ere then related to each other 
by the second method. None of the samples contained a very smell pro- 
portion of one ingredient, so that several eauetions ^ere eauelly 
applicable, one of them being (140.714A) E=56.1, from which the 
intensity of synergism ,rr as 40. 
Kilgore (160) in United States Fatent 2,149,917 issued in 1939, 
claims a process '-hich corn-prises the extraction of rotenone and other 
compounds having insecticidal properties from rotenone-bearin.j -plants 
by means of an ester belonging to the class of organic compounds kv 
as delte-epsilon-unsetarated-elphe-gemma-diket: carboxylic esters of 
the general formula: 
R, 
R l- 
'4 
>=C-C0-CH2- CO-COOR3 
^'herein R-j_ end Fvg ere the seme or different organic radicals or 
respectively one organic radical and one hydrogen atom, R^ i s an 
alkyl radical or a hydrogen atom, and R 7 is env organic radical form- 
ing an ester of the carboxj'! group. Not only do these <?ste-rs effectively 
extract rotenone from such plants but they carry the extracted r:tenone 
into solution in spreyable vehicles, 'such as hydrocarbon solvents, thus 
effecting a direct transfer of the rotenone from the plent to the final 
insecticide solution. Tests e^einst houseflies '--ere made "ith extracts 
