60 BULLETIN 824, U. S. DEPARTMENT OF AGRICULTURE 
energetically. Solutions of the powder made with water or with 
dilute alcohol were found to be entirely inactive. 
Dal Sie (60), in 1879, claimed to have proven the presence of a free, 
easily volatilized acid which was found in the ethereal, alcoholic, or 
aqueous extracts of the powder. From the ether extract of the flowers 
he obtained not only a crystallizable acid, but also an aromatic 
smelling acid of oily consistency at ordinary temperature. From 
the alcoholic extract he obtained a resinous matter resembling a 
glucoside, probably the same as that found by Rother, since under 
the influence of dilute sulphuric acid it split up into sugar and another 
product. According to Dal Sie, smce the fumes which result from 
the incomplete combustion of imsect powder exhibit the toxicity 
of the original powder, the toxic principle must be volatile without 
decomposition, and the free volatile acid is, therefore, the most 
active constituent of Pyrethrum. 
Textor (272), 1881, as the result of his tests, stated that ‘‘the 
active principle of Persian insect powder is, in nature, a soft resin.” 
He pulverized (80-mesh) 114 ounces of whole flowers (species not 
indicated), and percolated the powder with benzine for six hours, 
using 6 fluid ounces. The benzine solution was evaporated, water was 
added, and the product was again evaporated to remove any volatile 
oil. The residue was treated with dilute acid and filtered. No alkaloid 
could be detected in the filtrate by phosphomolybdic acid, Mayer’s 
reagent, or a solution of iodin in potassium iodid. The benzine ex- 
tract, the benzine extract in alcohol precipitated by acid, and the benzine 
extract in caustic potash and precipitated by acid, were all poisonous 
to flies. The benzine extract in aicohol was acid to litmus. A test 
for essential oil was made by allowing the powder to stand in dilute 
salt solution for 24 hours and then distilling, but none was obtained. 
Hirschsohn (133), in 1890, found that alcohol, ether, chloroform, 
or benzine would dissolve the active principle of insect powder. 
The extract obtaimed with these solvents, when added to an inactive 
powder, e. g., powdered chamomile, produced a powder as active 
as the original insect powder before extraction. From the work 
of Hirschsohn, the active principle would appear to be nonvolatile, 
as he found samples of powder which had stood for five years in paper 
boxes still as active as fresh powder. Heated at 120° F. insect powder 
lost its odor, but was as active as ever against flies. To see if the 
active principle was acid in nature, he treated powder with alcoholic 
ammonia, also with alecholic potash, but after drying in the air the 
powder was as active as ever. Placed for 24 hours in water, the water 
became acid, but the powder after drying was still active. 
Gillette (96), in 1889, ‘arrived at the same conclusions as to the 
absence of toxic substances in the volatile oil of Pyrethrum. He 
made practical tests upon insects, operating as follows: | 
Two or three grams of the powder were first put in a test tube and the dust allowed 
to settle for a few minutes. Then a loose cotton plug was pushed halfway down 
in each, upon which were placed the insects, and the tubes were then tightly 
corked. Dipterons, ichneumons, chalecids, cynipids, and aphids were subjected 
to this treatment and allowed to remain for different lengths of time, varying from 
1 or 2 to 40 hours, without showing any signs of being affected by the volatile oil. 
To see if the toxic principle of Pyrethrum would come off at a 
higher temperature, Gillette made further tests: 
Two cynipids were then similarly inclosed in a tube with fresh powder and the 
lower end of the tube was held for 10 minutes in a dish of boiling water, the upper 
