So TROPICAL MEDICINE AND HYGIENE 



to cause symptoms. Many persons will take this dose 

 daily during their whole residence of one year in Africa 

 and have no fever at all, but if they discontinue it on 

 the way home, or on arrival in England, within two or 

 three weeks after they have ceased to take it they get 

 fever, showing that this dose had not prevented infection. 

 It also has little effect in reducing the number of crescents 

 already formed. In children quinine tannate, i or 2 gr., 

 made up with chocolate is effective and is readily taken. 



Of the methods of administration at longer periods 

 there are many variations : 10 or 15 gr. once or twice 

 a week is advocated by some ; 10 or 15 gr. on the ninth 

 and tenth, twentieth and twenty-first, and last two days of 

 each month is preferred by others. Thomson advocates 

 the daily use of 20 gr. for a period of three. weeks four 

 times a year. This dose, he contends, kills off both the 

 sexual and asexual forms, and would free the population 

 from the parasites. In isolated places, where the plan 

 could be adopted simultaneously for the whole popula- 

 tion, the method is well worth a trial. 



With large stations the most satisfactory results are 

 obtained by diminishing the number of the definitive 

 hosts, anophelines. The most vulnerable period in the 

 life-history of these insects is in their larval stage. This 

 is always passed in water. A somewhat detailed know- 

 ledge of the class of breeding-place for the species that 

 carry malaria in each place is required for effective and 

 economical work in this direction. As these places differ 

 for each species of mosquito, without detailed knowledge 

 money will be wasted and the results cause disappointment. 



It is important to have both the coolie lines and the 

 European quarters at some distance from each other, so 

 that infected anophelines cannot readily pass from one 

 to the other, and that both should be well in the culti- 

 vated, cleared and drained area where the number of 

 anophelines has been reduced. 



Wet methods of cultivation, such as that required for 

 rice growing or such cultivation as requires an extensive 





