1 88 Arthropods as Hosts of Pathogenic Protozoa 



The clearest early presentation of the circumstantial evidence in 

 favor of the theory of mosquito transmission was that of A. F. A. 

 King, an American physician, in 1883. He presented a series of 

 epidemiological data and showed "how they may be explicable by 

 the supposition that the mosquito is the real source of the disease, 

 rather than the inhalation or cutaneous absorption of a marsh vapor." 

 We may well give the space to summarizing his argument here for 

 it has been so remarkably substantiated by subsequent work: 



1. Malaria, like mosquitoes, affects by preference low and moist 

 localities, such as swamps, fens, jungles, marshes, etc. 



2. Malaria is hardly ever developed at a lower temperature 

 than 60 Fahr., and such a temperature is necessary for the develop- 

 ment of the mosquito. 



3. Mosquitoes, like malaria, may both accumulate in and be 

 obstructed by forests lying in the course of winds blowing from 

 malarious localities. 



4. By atmospheric currents malaria and mosquitoes are alike 

 capable of being transported for considerable distances. 



5. Malaria may be developed in previously healthy places by 

 turning up the soil, as in making excavations for the foundation of 

 houses, tracks for railroads, and beds for canals, because these opera- 

 tions afford breeding places for mosquitoes. 



6. In proportion as countries, previously malarious, are cleared 

 up and thickly settled, periodical fevers disappear, because swamps 

 and pools are drained so that the mosquito cannot readily find a place 

 suitable to deposit her eggs. 



7. Malaria is most dangerous when the sun is down and the 

 danger of exposure after sunset is greatly increased by the person 

 exposed sleeping in the night air. Both facts are readily explicable 

 by the mosquito malaria theory. 



8. In malarial districts the use of fire, both indoors and to those 

 who sleep out, affords a comparative security against malaria, because 

 of the destruction of mosquitoes. 



9. It is claimed that the air of cities in some way renders the 

 poison innocuous, for, though a malarial disease may be raging out- 

 side, it does not penetrate far into the interior. We may easily 

 conceive that mosquitoes, while invading cities during their nocturnal 

 pilgrimages will be so far arrested by walls and houses, as well as 

 attracted by lights in the suburbs, that many of them will in this 

 way be prevented from penetrating "far into the interior." 



