154 SEGREGATION [CH. 



In addition to this direct action of quinine upon the source 

 of infection in man, there are a number of indirect methods of 

 reducing the sources of infection. 



3. (a) Very often where mixed communities are con- 

 cerned, it may be desirable to protect especially the more 

 susceptible class of individuals. When possible this is brought 

 about by some form of segregation. Where the reservoir of 

 virus is small in comparison with the community of susceptibles, 

 as frequently happens in Algerian stations, segregation takes 

 the form of removal of the indigenous community to a short 

 distance from the station. Where the number of the suscep- 

 tible persons is small in comparison with the reservoir, as is 

 usual in the case of Europeans in Africa, it is advisable to build 

 quarters for this community at some distance from the native 

 settlement. In some cases it may be desirable to undertake 

 measures against malaria in a small community acting as a 

 " reservoir," not so much for the direct effect upon this com- 

 munity, as for the indirect effect upon the larger susceptible 

 community surrounding it. In this way, the actual application 

 of segregation may vary, though the principle remains the 

 same. 



Still another indirect method of diminishing the amount 

 of human infection, and thus reducing the activity of malaria 

 transmission, is the protection of a community from influences 

 likely to bring about repeated relapses. For example, among 

 labourers or convicts, or even among agricultural people, any 

 amelioration of the conditions under which they are living may 

 be looked upon as an anti-malarial measure coming under this 

 head. 



(b) Protection against the bites of Anopheles by the 

 screening of dwellings with wire gauze, etc. is a measure which 

 has been found especially valuable in Panama and elsewhere. 

 The protection brought about by the habitual and careful use 

 of a mosquito net is perhaps the most effective measure of 

 private prophylaxis known against malaria, and with some 

 other minor precautions is quite sufficient to enable the educated 

 individual to enter the most malarious tracts unharmed. The 

 use of mosquito nets by the sick is a valuable prophylactic 



