72 BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE. 
extract was shaken up with water until entirely free from water- 
soluble substances. The residue was then dissolved in ether, the 
part insoluble in ether being treated with potassium hydroxid solu- 
tion, and this then shaken out with ether. The deep-green ethereal 
solution was freed of chlorophyll, etc., by shaking with 10 per cent 
caustic-potash solution until the dark green turned to a yellow brown 
and the alkaline solution was entirely colorless. The ether solution 
was then shaken out once with dilute sulphuric acid, then with water, 
and finally the ether distilled off. This left a clear, yellow-brown mass 
which gave a neutral reaction and had a sharp and bitter taste and 
the characteristic odor of insect powder. The yield of this material 
was 1.4 per cent of the original material. For further purification 
the substance was dissolved in a little ether mixed with a large 
amount of petroleum ether, filtered, warmed with animal charcoal, 
and again filtered, and the petroleum ether then evaporated. A 
yellow sirupy mass was left, which had only a feeble odor, and a 
taste bitter at first and then intensely sharp. It gave a neutral 
reaction, was soluble in alcohol, ether, etc., but was insoluble in 
water, acids, and alkalis. It contained no nitrogen. This substance, 
which seems to be an ester, Fujitani calls pyrethron, and it is, accord- 
ing to him, the active insecticidal principle of Pyrethrum. Pyre- 
thron decomposes even on standing, yielding pyrethrol, which ap- 
pears to have the formula C 21 H 34 O. Tested upon different animals, 
pyrethron showed an action similar to that of veratrine. Fish and 
insects were very susceptible but protozoa very tolerant. On warm- 
blooded animals it caused epileptiform convulsions, increased 
blood pressure, and increased breathing movements. 
Reeb (214), 1909, criticized Fujitani's work, arguing that treat- 
ment of the alcoholic extract with such powerful reagents as 10 per 
cent solution of potassium hydroxid and sulphuric acid might change 
bodies dissolved in the alcohol. Therefore it is not certain that the 
final product obtained by Fujitani, although toxic, is the real active 
preexisting principle. Reeb extracted Dalmatian insect powder 
with petroleum ether (specific gravity, 0.670). The petrolic liquids 
were filtered and evaporated, leaving a soft residue which represented 
3.50 per cent of the powder employed. This was treated with suc- 
cessive quantities of hot alcohol in the presence of a little animal 
charcoal. The alcoholic solutions were filtered and allowed to stand 
about a month, at the end of which time a resin (melting point, 125°) 
had deposited. This resin Reeb calls pyrethresine. From the alco- 
holic solution Reeb separates pyrethrotoxic acid by evaporating to 
dryness, taking up in acetone, adding barium carbonate, evaporat- 
ing to dryness, taking up in water, decomposing with sulphuric acid, 
and shaking out with ether, which upon evaporation leaves the pyre- 
throtoxic acid. From this work, therefore, Reeb verifies the work of 
