MOSQUITOES 71 



been learned from experience that by moving to high, 

 dry situations malarial fevers may be avoided. The 

 disease has been attributed not so much to the water as to 

 the so-called miasmatic airs that arise from the water and 

 wet soil. In fact, malaria means bad air. Not long 

 ago the writer heard a person object to building a house 

 in a certain valley-like depression because the cold, damp 

 air might cause malaria. It is a common precaution 

 against malaria to go within doors at early dusk and remain 

 until daylight, for the purpose, it is thought, of escaping 

 the damp, fever-giving atmosphere. 



It is true that there is a definite relation between 

 malaria and low lands, swamps, stagnant water, marshes, 

 and exposure out-of-doors at night in which people have 

 believed so long. The relation, however, results from a 

 very different agent than has been generally supposed 

 heretofore. Within the last few years, it has been con- 

 clusively and repeatedly demonstrated that malaria is 

 conve3 r ed to human beings and communicated to the blood 

 by mosquitoes and not by miasmatic airs arising from 

 swamps and marshes. The question immediately arises, 

 how does this accord with the relation of malaria to low 

 lands, marshes, swamps, stagnant water, exposure at 

 night, and the like ? The facts as we now know them 

 give the answer. We now know, by scores of investiga- 

 tions, that mosquitoes can exist only where there is 

 water ; that they are abundant in swamps, marshes, and 

 low lands, and that they (malarial mosquitoes) fly and 

 inflict their bites mainly at night and that they are not 

 usually present in high, dry situations. 



Our next great proof of the relation of mosquitoes to 

 malaria is the fact that the germ causing malaria has been 



