198 MOSQUITOES 



factory than the cheapest petroleum, and none of them 

 are recommended. In a work of this kind we need not 

 only the best but also the cheapest substances. The lars"e 

 scale on which this work is undertaken, and will be under- 

 taken in the future, demands a cheap substance, and on 

 the whole there can be no doubt that the kerosene known 

 as fuel oil will be found to be the most satisfactory. Of 

 course, the general interest in the subject ■will induce 

 future additional exi^erimentation, and it is quite within 

 the possibilities that something better will be discov- 

 ered. Up to the present time, however, nothing definite 

 is known. 



The AM if ion of Breedhig- Places hy Drainage or by 

 Filling. 



In the chapter on mosquitoes and malaria is given an 

 account of how, by an expenditure of forty dollars for 

 drainage in the summer of 1900 in a Maryland village, 

 malaria practically ceased to exist, although the previous 

 summer there had been one or more cases in every family 

 in the village. That meant that the breeding-places of 

 Anopheles were abolished. And it should be added that 

 the numbers of mosquitoes of the genus Culex were vastly 

 reduced by this operation. Those which remained prob- 

 ably bred in artificial water-receiitacles, such as tanks, 

 tubs, or barrels, not a part of the former permanent supply 

 of the place. This is probably one of the most striking 

 instances of the value of drainage with which this section 

 could appropriately be introduced. 



