Oct. 16, 1916 
Effects of Nicotine as an Insecticide 
trate this point. These tracheal walls certainly were not much harder 
than the other tissues, because they stained more deeply than did the 
older chi tin. Plate 3, figure O, represents another trachea of the wax 
moth, showing an older chitinous fracheal wall; the nicotine did not pass 
into this wall. Plate 3, figure P, represents a small portion of the integu¬ 
ment (ini) of an aphid, showing that the pure nicotine did not pass into 
the chitin. Plate 3, figures N and Q, illustrates how well Camoy's fluid 
penetrates hard chitin. The black dots in the illustrations (pr) are crys¬ 
tals of mercuric chlorid that have remained after the fixative was removed. 
Plate 3, figure N, represents a trachea from a wax-moth larva, and Plate 
3, figure Q, a portion of the integument (inf) and fat cells (fc ) from an 
aphid. Attention is called to the mechanical or physical changes brought 
about in the fat cells by the fixation. Live fat cells never have a netlike 
appearance, but appear more or less granular, and usually# contain many 
globules. Sections from other insects that had been fixed in Carnoy’s fluid 
showed better than does figure Q the ability of this fluid to penetrate the 
integument. In a few cases the crystals lie in rows penetrating the integu¬ 
ment, indicating that the fluid had passed through the chitin in streams. 
If the most important results recorded under this large heading are 
briefly summarized, the following conclusions may be drawn: (1) Nico¬ 
tine spray solutions neither enter the spiracles nor pass through the 
integuments of insects; (2) nicotine as a stomach poison seems to be 
distributed to all the tissues, including the nervous system; (3) nearly 
all the nicotine fumes that strike the integuments and pass into the 
tracheae are immediately condensed, so that in regard to nicotine as a 
fumigant the integuments and tracheal walls are more or less covered 
with fine spray; (4) this fine spray is well distributed through the 
many small tracheal branches to all the tissues, where some of it passes 
into the cells; (5) the nervous system receives its quota of the fine spray 
and vapors from the spray, which immediately paralyzes the nerve cells; 
(6) the statement just preceding explains how odoriferous particles and 
vapors from nicotine spray solutions kill insects by paralysis. 
HISTORICAL REVIEW 
After making a few remarks concerning the chemistry and properties 
of nicotine, a brief review pertaining to the pharmacological effects of 
nicotine on various classes of animals, and a few other observations by 
the writer will be given in order that these results may be compared ^ith 
those obtained on the insects discussed in the preceding pages. 
(l) GENERAL REMARKS ABOUT NICOTINE 
Nicotine (C 10 H 14 N 2 ) was conclusively prepared synthetically by Pictet 
and Rotschy (19) in 1904. This investigation concluded a long series 
of works pertaining to the structure of this deadly poisonous alkaloid. 
These authors showed that it is a pyridin-methyl-pyrrolidin. 
