34 
Poisonous Arthropods 
species and insects transmitting disease, we shall discuss here only 
the poison of the mosquitoes. 
It is well known that mosquitoes, when they bite, inject into the 
wound a minute quantity of poison. The effect of this varies accord¬ 
ing to the species of mosquito and also depends very much on the 
susceptibility of the individual. Soon after the bite a sensation of 
itching is noticed and often a wheal, or eminence, is produced on the 
skin, which may increase to a considerable swelling. The scratching 
which is induced may cause a secondary infection and thus lead to 
serious results. Some people seem to acquire an immunity against 
the poison. 
The purpose of this irritating fluid may be, as Reaumur suggested, 
to prevent the coagulation of the blood and thus not only to cause 
it to flow freely when the insect bites but to prevent its rapid coagula¬ 
tion in the stomach. Obviously, it is not developed as a protective 
fluid, and its presence subjects the group to the additional handicap 
of the vengeance of man. 
As to the origin of the poison, there has been little question, 
until recent years, that it was a secretion from the salivary glands. 
Macloskie (1888) showed 
that each gland is sub¬ 
divided into three lobes, 
the middle of which differs 
from the others in having 
evenly granulated contents 
and staining more deeply 
24. Diagram of a longitudinal section of a mosquito. 
than the others (fig. 24). This middle lobe he regarded as the source 
of the poison. Brack, (1911), by the use of water, glycerine, chloro¬ 
form, and other fluids, extracted from the bodies of a large number 
of mosquitoes a toxine which he calls culicin. This he assumes 
comes from the salivary glands. Animal experimentation showed 
that this extract possessed hemolytic powers. Inoculated into the 
experimenter’s own skin it produced lesions which behaved exactly 
as do those of mosquito bites. 
Similarly, most writers on the subject have concurred with the 
view that the salivary glands are the source of the poison. How¬ 
ever, recent work, especially that of Nuttall and Shipley (1903), 
and Schaudinn (1904), has shown that the evidence is by no means 
conclusive. Nuttall dissected out six sets (thirty-six acini) of glands 
from freshly killed Culex pipiens and placed them in a drop of salt 
