177 
ON THE ABSENCE OF A VESICANT 
IN THE ETHER EXTRACT OBTAIN¬ 
ABLE FROM MOSQUITOS 
BY 
J. O. WAKELIN BARRATT, M.D., D.Sc., London. 
(Received for publication 6 June, I 9 10 ^ 
The bites of mosquitos arc well known to cause a more or less 
troublesome degree of irritation of the skin, which commences at 
the end of a few hours, and lasts from one to three days or more. 
The skin in the immediate neighbourhood of the bite becomes 
reddened, itchy and slightly swollen. If rubbed a wheal is 
generally readily produced. The degree of irritation varies with 
different individuals. Those who have lived long in mosquito- 
infested districts not unfrequently describe themselves as having 
become quite or nearly immune to mosquito bites. 
The cause of this irritative effect of the bite of the mosquito is 
presumably to be found in the fluid injected by it into the skin 
when sucking blood.* The nature of the effective constituent of this 
fluid has not yet been determined and, owing to the small size of 
the mosquito, investigation is attended with difficulty. 
The experiments which form the subject of this paper were 
made with a view of ascertaining if any substance possessing 
irritating properties when applied externally to human skin was 
present in the extract obtainable from mosquitos with the aid of 
ether. It is well known that in the Spanish Fly {Lytta vesical ana) 
a strong vesicant, cantharidin, is present, in amount, equal, it 
may be, to as much as 2 per cent, of the dried insect. Although 
the present investigation failed to reveal the existence of an} 
irritant in mosquitos, similar to that present in Lytta vesicalona , it 
•F. Schaudinn (Generations und Wirtswechsel bei thecoiUCTiS^f the 
Arb. aus dem Rais. Gesundheitsamte, 1904. Bd. 20, S. 419), bin s ‘ . probably by the 
oesophagus of the mosquito are effective in causing irritation of t I - 
agency of the fungi they contain. The salivary glands are not irritant. 
