PROBLEMS AND PRINCIPLES OK MALARIA PKEVKXTION. ly/ 



chemicals, etc. All these points must be given due considera- 

 tion, and the campaign must be so planned as to secure the maxi- 

 mum of effect at the minimum of inconvenience to the population 

 and damage to property, and at a cost consistent with the re- 

 sources of the people and with the improvement in health, as well 

 as probable increase in land and property values, which may 

 reasonably be anticipated. Filling, various drainage schemes, 

 deforestation, grass cutting, training of stream banks, oiling and 

 treatment with chemicals, all have their proper uses, and all must 

 be considered. 



(3) The Protection of the Individual against Mosquito 

 Bites. — Under this head come — 



(a) The ofticient screeninti nt dwellings. 



(b) Tile catching of inosquit')s within dweUings 

 (t") The nse of mosquito nets over heds. 



The effectiveness of these measures depends upuii the 

 principle that most bites by infective mosquitos occur at night. 

 The value of these ])rotective measures is in the order I have 

 stated them, but one cannot hope to effectively protect a fixed 

 population by the adoption of either or all of these. At best, 

 they are merely measures of amelioration, and their fields of 

 usefulness are temporary hal)itations, such as camjis. military or 

 civilian, isolated farms and individual households in a com- 

 munity non-progressive enough to delay undertaking public 

 measures for its protection against malaria. 



A few words in connection with the use of mosquito nets 

 and the screening of houses. I have seen, times without number, 

 nets hung over beds in such a manner that instead of being a 

 protection to the sleepers, they were a menace. It is not suffi- 

 cient to merely drop the net over the bed, on the outside of the 

 frame. The net must be tucked in carefully all around tmder 

 the mattress inside of the bed frame, and the net must be abso- 

 lutely free from even the smallest of tears. It is a fact that 

 mosquitos will enter through a very small ajXM-ture in search of 

 food, but do not seem to be able to find their way out again. 

 On this fact rests the princi])le of most mosquito traps. The 

 bed must be reasonably wide, so that the sleeper would not be 

 fairly certain to lie close to the net and be bitten through it. 

 One must make sure also, before tucking in the net. that there 

 are not mosc[uitos within it. 



To make a house mosquito-proof requires ver\' careful plan- 

 ning and a good deal of special knowledge. Most houses that 

 are supposed to be mosc[uito-proof are merely mosc|uito traps. 

 A few e>sential points are : — 



The mosquito gauze must have sufticiently small meshes to 

 prevent mos([uitos from crawling through ; 256 to 324 to the 

 s(|uare inch are usually required, or what are known as 16- and 

 18-mesh gauze respectively. The exact size de])ends on the 

 prevalent sjjccies of mosquitos. B}- choosing gauze made of 

 pure cop|)er or bronze, and thus securing the maximum of open 



