170 THOMPSON YATES LABORATORIES REPORT 
Before discussing in detail the special methods of prevention which promise 
success in Africa, it will be well to briefly pass in review the main lines upon which 
malaria may be combated. 
There are three main directions in which we may hope to influence malaria : 
1 To attempt to destroy anopheles, either by doing away with the pools 
they breed in, or by destroying the larvae or adults. 
2 To attempt to so protect men that anopheles cannot infect them, as by 
the use of mosquito nets or mosquito-proof houses. 
3 To attempt to destroy the parasite in man himself, so that even though 
anopheles are present malaria is still absent. 
The first and second methods appear at first most likely to lead to success. 
Recent researches, however, have shewn that the third method is a most effective 
way of dealing with the problem. 
It may be pointed out that it appears to have been in this latter way that 
malaria has disappeared from the fen districts of England. Anopheles are still widely 
distributed, but there is no malaria. The probable explanation is that extensive use 
of quinine by the inhabitants of these districts has led to this result, and that the 
method Koch employed of combating malaria in New Guinea by quinine was 
unwittingly the cause of the disappearance of malaria in England. 
I. THE DESTRUCTION OF ANOPHELES 
The Superficial Drainage of an Area. Such a method can evidently be applied 
only to very limited areas. Even in Europe it would be difficult of application apart 
from towns, whilst in Africa there can be no question of its application except under 
certain special conditions. Even in most African towns drainage would be by no 
means a light task. In Lagos draining or filling up possible anopheles pools would 
be a gigantic undertaking. In Accra, situated on porous soil with an extremely 
scanty rainfall, it would not be so difficult. Even in Accra, however, it would 
probably only be possible after a water supply had been brought from the Aburi 
hills, for at the present time many of the inhabitants depend for water upon the very 
pits and wells which act as breeding-places. In Freetown, which is built on rock, 
the central parts of the town might be rendered free from all pools, yet the outskirts 
could not be so treated without great outlay. 
Surface drainage in Africa must then be considered essentially of limited 
application. It is, indeed, only feasible when applied to a segregated community of 
Europeans. Such a special use of drainage is evidently by no means the enormous 
operation involved in draining a town of many thousands of inhabitants. 
The Application of Culicicides. Great expectations were at one time held as to 
the efficacy of this method. In Africa the result of its application has not been 
