- 5 - 
It contained slightly less than 3 percent of nicotine and for many years 
was more efficient and more widely us«*d than any other form of nicotine. 
During the next decade 11 more preparations were introduced, half of 
which proved to be excellent insecticides. A few of these are still being 
used| In 1908 a patent was granted covering a method of producing a con- 
centrated solution of nicotine sulfate containing as much as 40 percent of 
nicotine. This sulfate was first called Nico-Sul, but in 1910 it was placed 
on the market under the name of Black Leaf 40, From 1911 to 1920 about 22 
additional proprietary insecticides were introduced, three-fourths of which 
were foreign, A new type of nicotine-bearing dustj called Nicodust, was 
first placed on the market in 1920, From 1921 to 1934, 16 more trade names 
were added to the list. Those most frequently found in the literature 
include Nico-Fumc Fumigating Powder (1922), Vapona (1933), Black Leaf 50, 
ar.d Black Leaf 155 (1934). 
Other Nicotine" Preparations 
In America dependence has been largely upon the proprietary prepara- 
tions, but in Europe, particularly in France and Germany, the proprietary 
products seem not to have been widely used, chiefly because the preparation 
of nicotine insecticides was controlled by the government. The State 
factories of France in 1909 prepared ordinary tobacco juice and titrated 
juice for the agriculturists. The nicotine content of the former depended 
on its density v/hich, since 1882, was determined by a hydrometer in degrees 
Baumel The titrated juice, containing sulfates of nicotine and sodium and 
organic salts, rath a nicotine content of 10 percent, was sold as titrated 
nicotine. In 1924 the French Government issued nicotine in three forms — 
ordinary juice, an extract containing nicotine sulfate, and condensed 
juice (a mixture of the other two), 
IV. HOW NICOTINE KILLS INSECTS 
A little casual information on the physiological effect of nicotine 
is to be found in numerous papers from 1895 to 1934, but only a few studies 
were originally planned to determine how nicotine kills insects. A few. 
other papers give additional information which is probably correct but not 
supported by experiments. It was the fundamental information on this point 
that led to the preparation and use of nicotine dust. 
The symptoms of nicotine poisoning in the experiments with bees in 
1916 were, divided into three stages. First, bees that had eaten nicotine 
soon became abnormal in behavior, and the legs and wings were partly paralyzed. 
Second, the paralysis progressed from partial. to complete, the hind legs 
and hind wings usually being the first to be completely paralyzed, then 
followed the middle legs and front wings, and, finally the front legs. Third, 
the bees wore apparently dead except for slight movements of the head appen- 
dages, legs, and abdomen. Regardless of how nicotine is applied, it seems 
to kill by motor paralysis; that is, it first affects the nerve centers that 
control muscular movement. Its action on the motor centers causes complete 
paralysis, which is supposed to be brought about by absorption of the 
nitrogen atom of the poison by the nitrogen-fat compounds that make up the 
nerve tissue, with the result that further absorption of oxygen by the cells 
is stopped and the insect is killed. Since 1916 the word "paralysis" has 
been repeatedly used in connection with the effects of various insecticides, 
but incorrectly, perhaps in most instances, because there are very few 
insccticidal nerve poisons. 
