POISON OF MOSQUITO-BITE 317 



a poisonous saliva was introduced. He noticed that if the mosquito punctures 

 the skin without entering a blood vessel, although it may insert its proboscis 

 for nearly its full length, no poisonous effect is produced upon the skin, but 

 when the proboscis strikes blood and the insect draws it, the subsequent swelling 

 and poisonous effects are obvious. He argued that these effects indicate a con- 

 stant outpouring of some sort of poisonous fluid during the blood-sucking 

 process. 



Miall (1895) maintains that it can not positively be said whether poison is 

 injected into the wound or not. His statement is, " No poison gland has hitherto 

 been demonstrated, and there is some reason to believe that the irritation of the 

 wound is slight in cold weather and only becomes intense during great summer 

 heat.'' But in our chapter on the anatomy of mosquitoes we have shown that 

 Maclosky has demonstrated a differentiation in the salivary glands, one of each 

 set being modified to secrete the poison. Fritz Schaudinn is inclined to believe 

 that the mosquito bite is poisonous not because of any poisonous secretion of the 

 salivary glands, but because of toxins produced by plant parasites in its 

 cesophageal diverticula. 



The purpose of the mosquito poison has been the subject of some conjecture. 

 The old Reaumur hypothesis, that it causes the blood to become more liquid and 

 more readily sucked up by the mosquito, has had its adherents. Osten Sacken 

 and Miall, however, believe that it is probable that the piercing mouth-parts of 

 the mosquito were originally acquired for the purpose of sucking the juices of 

 plants, and Maclosky advances the idea that the chief food of mosquitoes is not 

 animal blood but the proteids of plants, and that probably the poison injected 

 may prevent the coagulation of proteids and so promote the process of suction. 



Prof. John B. Smith was inclined to believe in the Eeaumur hypothesis, that 

 the poison prevents the clotting of the blood in the stomach of the mosquito. 

 He says : 



"A mosquito bites, primarily to obtain food; there is neither malice nor 

 venom in the intent, whatever there may be in the act. Theoretically there 

 would seem to be no reason why there should be any pain from the introduction 

 of the minute lancets of the insects, and the small amount of blood-letting is 

 usually a benefit rather than otherwise. Unfortunately, however, in its normal 

 condition the human blood is too much inclined to clot to be taken unchanged 

 into the mosquito stomach; hence, when the insect bites, a minute droplet of 

 poison is introduced, whose function it is to thin out the fluid and make it more 

 suitable for mosquito digestion. It is this poison that sets up the inflammation 

 and produces the irritation or swelling. If we make a puncture wound with a 

 fine needle, a small droplet of blood will exude which will almost at once harden 

 into a clot, and if we attempt a little later to break that clot, we will find it tough 

 and hard to disintegrate. If we allow a mosquito to bite until it Is fully gorged 

 and then smash it, we find that the blood from the gorged abdomen is much 

 more fluid and spreads out thin. If we further allow it to dry, there will be no 

 clot ; but a thin spread of material which is brittle and breaks readily into frag- 

 ments. 



" The pain is caused entirely by the action of the poison in breaking up the 

 blood, and as the first act of a biting mosquito is to introduce this poison into 

 the wound, the pain and inflammation will be the same, whether the insect gets 



