352 



Breathing 

 tubes 



Comtain Care Is Needed for Health unit vi 

 Eggs 



Fig. 312 The life history of 

 the cominon mosquito (Cu- 

 lex) . All mosquitoes develop 

 in much the same way. How 

 can such inforfnation help in 

 the control of juosquitoes? 



was long suspected that the disease was 

 carried by mosquitoes, but since no trace 

 of the microorganism could be found in 

 either man or mosquito, the theory at 

 first was not taken very seriously. We 

 now know why the cause could not be 

 found; a virus causes the disease. After 

 long study and much unsatisfactory ex- 

 perimentation with mosquitoes, carefully 

 controlled experiments performed by Dr. 

 Walter Reed and others brought results. 

 When a call went out from the United 

 States Army for volunteers for these ex- 

 periments a private, John R. Kissinger, 

 was the first to allow himself to be bitten 

 by yellow fever mosquitoes which had 

 sucked the blood of a yellow fever pa- 

 tient. In later experiments John J. Aloran 

 also allowed infected mosquitoes to bite 

 him. Both men came down with bad 

 cases of yellow fever, suffered horribly 

 for days but finally recovered. Kissinger 

 paid more heavily for his sacrifice for he 

 never fully regained his health. In the 

 meantime three other men of the hospi- 

 tal staff had volunteered for die other 



Larva ("wriggler") 



part of the experiment. They slept for 

 twenty nights in a screened hut, using 

 the bedding and belongings of patients, 

 some of whom had just died of yellow 

 fever. They had the best of the bargain 

 for, as events proved, the organism caus- 

 ing yellow fever cannot enter the body 

 except through the bite of a mosquito. 



These were the first of the experi- 

 ments which later definitely proved that 

 only yellow fever mosquitoes can carry 

 the virus from one person to another. 

 Once this had been established, it was 

 clear that the way to keep yellow fever 

 from spreading is to destroy the mos- 

 quitoes. 



Mosquito extermination. Evidently 

 mosquitoes in many parts of the world 

 are not only a nuisance but a menace to 

 health. The problem of mosquito exter- 

 mination is, therefore, a pressing one. 

 Mosquitoes lay their eggs on still or 

 slowly moving water. The eggs hatch 

 into tiny larvae called wrigglers. In time 

 these develop into active pupae which 

 also live in the water. Both larvae and 



