CONDITIONS INFLUENCING PREVALENCE 217 



high a price to pay, even for immunity from fever. On 

 the other hand there are many places where the number of 

 possible breeding places are small in number and limited in 

 extent, and where accordingly immunity can be secured 

 at very trifling trouble or expense. The instance of the 

 successful use of kerosme as a larvicide thirty years ago, 

 in America, quoted in the first edition, must have been an 

 extreme example of this. In this case, L. 0. Howard 

 ("Insect Life," vi, p. 90) describes how a residence was freed 

 from Mosquitoes by killing the larvae in a single pool some 

 4,000 feet square. In by far the majority of places the 

 experiment would, at best, have proved but partially success- 

 ful, owing to the existence of alternative, but unsuspected 

 breeding places. 



To mention another instance : There is, I have no hesita- 

 tion in stating, no good reason why the European residents 

 of most stations in Upper India should be much troubled by 

 Mosquitoes in the hot weather. The fierce, dry heat has 

 dried up every possible natural breeding place, and the 

 swarms of Mosquitoes that render life a burden are bred 

 exclusively in the garden tanks described above, and in 

 other easily discoverable domestic collections of water. If 

 each resident would devote a few minutes once a week to 

 seeing that his servants emptied these and carefully 

 cleaned them out, the nuisance would be reduced to a 

 minimum. Moreover, in many places the individual houses 

 are so scattered that a considerable degree of personal 

 immunity may be secured by attention to one's own bunga- 

 low alone. 



As the quarter in which they reside is usually quite 

 isolated from the houses of natives other than their own 

 domestic servants, the area is entirely under their own 

 control, and all that is required is a little friendly co- 

 operation. 



From what has been said it will, I think, be clear that 

 it is impossible to prescribe any generally applicable method 

 of dealing with malaria by radical measures intended to 

 diminish the prevalence of Mosquitoes, and success can only 

 be hoped for by a careful study of local conditions, guided 



