CONDITIONS INFLUENCING PREVALENCE 225 



that, not being volatile, its action is much more permanent, 

 lasting for as long as two months, and there can be no 

 doubt that it should be at least given a thorough trial. 

 Assuming it to stand the test of practical work in the open, 

 the question whether this or kerosine will be the cheaper 

 agent to employ will depend on the depth of the water to 

 be dealt with, as the entire bulk of the water must be 

 rendered lethal ; whereas with kerosine depth need not be 

 considered, and superficies is all that need be taken count 

 of; so that where the water is shallow in proportion to its 

 surface, paraffin will certainly be the cheaper ; while 

 deep pools will be more economically dealt with by the 

 new agent, the more so as the chemical would probably 

 remain unaltered in the surface mud when it dried up, and 

 more or less of it would be still available when redissolved on 

 the reformation of the pool after fresh rain. 



It may be freely admitted taht in many places larvae- 

 bearing pools are so omnipresent that it may be practically 

 impossible to deal with them in this, or any other detailed 

 fashion, but it is equally true that many limited areas might 

 be dealt with at but little cost or trouble ; and it is to be 

 hoped that some of our Colonial Governments may see 

 their way to giving a fair trial to the methods above 

 indicated in some selected localities. 



Such being the state of our knowledge as to the sani- 

 tation of malaria on a large scale, it remains to be seen 

 what can be done in the way of personal hygiene ; and 

 here I believe it may be confidently asserted that much 

 may be accomplished, though not of course absolutely 

 without trouble, expense or other effort on the part of 

 those who wish to protect themselves against this disease. 

 Putting aside the prophylactic use of drugs, which may 

 be better left to purely medical treatises, personal hygiene 

 resolves itself into two classes of precautions, viz., by as 

 far as possible preventing Mosquitoes from breeding in the 

 immediate neighbourhood of our houses, and secondly, as 

 private efforts of the first category can be only partially 

 successful, to endeavour to avoid being bitten. 



Precautions of the first class have already been sufti- 

 15 



