Oct. 16, 1916 
Effects of Nicotine as an Insecticide 
US 
deep grooves. The paramecia were still alive when the nematodes be¬ 
came lifeless, but they finally died slowly and gradually and at no time 
showed any reaction which could be attributed to a stimulation. 
There are many papers dealing with the economic importance of 
nicotine as an insecticide, but they contain nothing about the pharma¬ 
cological effects of nicotine and little about its physiological effects, 
except that it is effective. 
So far as known to the writer, only two authors have anything to say 
about the pharmacological effects of nicotine on insects. 
Del Guercio (10) sprayed silkworms with various dilutions of nicotine 
and determined that this insecticide within a short time brings about con¬ 
vulsive movements in the caterpillars, causing them to fall from the plants 
and resulting in death in most cases. He thinks that nicotine spray solu¬ 
tions affect insects by means of the vapors from the nicotine poisoning 
them and that these vapors even in minute quantities cause irritation 
and convulsive movements which result in death by total paralysis. 
He made no histological study to ascertain what tissue is vitally affected, 
and his view is based solely on the behavior of the caterpillars treated. 
Shafer (20) ascertained that insects subjected to the vapors of nicotine 
and other contact insecticides first pass through a stage of excitement, 
then through a stage of depression in which the coordination of move¬ 
ments is uncertain, and finally through a stage in which there is total 
loss of movement and sensibility. The last stage was followed more or 
less rapidly by death. During the first stage the action of the heart was 
increased and was irregular, then it became depressed, but the heart 
action was one of the last visible signs of life to disappear. Secretions 
were also observed to issue from the mouths. The value of the respira¬ 
tory ratio arose, showing that these vapors depress the activity of 
oxygen absorption more than they do the ability of carbon-dioxid 
excretion. Shafer fouhd that the insects used continued to give off 
carbon dioxid when no oxygen was present to be taken up. Loeb (16) 
cites similar experiments in which muscles deprived of oxygen continued 
to give off carbon dioxid. 
Before discussing the pharmacological effects of nicotine on the verte¬ 
brates, the physiological classification of this alkaloid as defined by toxi¬ 
cologists may be given. Blyth (3, p. 269-279) places nicotine in that 
class of poisons affecting the nervous system which causes convulsive 
movements and complex nervous phenomena. Kobert (12) places nico¬ 
tine in that class of poisons affecting the cerebrospinal system which is 
able to kill without producing coarse anatomical changes. Brundage (4) 
classifies nicotine as a neurotic which depresses the cerebrospinal system. 
Blyth (3) says that small fish die within a few minutes from a milligram 
of nicotine. They are first stimulated, then become less active, and are 
rapidly paralyzed. 
