Dr Stephens, The Prevention of Malaria. 131 



But even did this occur it is quite clear that the risk is now very 

 largely diminished, for granted that occasionally an Anopheles did 

 fly this distance, the risk is very different from that encountered 

 in the midst of native quarters in which Anopheles may be caught 

 in hundreds or even thousands. 



But our experience of two years' residence in Africa, under 

 many different conditions, leads us most emphatically to deny that 

 the objection of the flight of Anopheles is at all a practical one. 

 Our experience for instance in Freetown itself absolutely con- 

 tradicts this. Now in the outskirts of Freetown, Anopheles exist in 

 myriads, and myriads of larvae are to be found in the pools. But 

 there is a central area of Freetown which has no pools and in 

 which houses (not huts) occur, and these are of stone and fairly 

 well lighted. We have at different times slept during some 

 months in five different houses in this area, and never have we 

 found an Anopheles on our mosquito net at night or at daybreak, 

 and we invariably searched at these times, and this is convincing 

 evidence that they were not present. Now if it be true that 

 Anopheles fly extraordinary distances as occasionally stated, we 

 should have found them in the centre of Freetown, but we never 

 did. Our experience at Accra was exactly similar. We there 

 occupied a bungalow, a quarter to half a mile from a native village, 

 but again we never observed a single Anopheles. 



This too brings us to the question of isolation of Europeans in 

 large towns which at first sight might seem to present considerable 

 difficulties, but we see from our experience in Freetown that such 

 isolation, to be effective, need not necessarily imply a separation 

 by a large distance. If under the worst conditions, even in towns, 

 the European quarter is well constructed and cleared of native 

 huts and provided with well-drained streets, then we shall find 

 that it will enjoy a considerable protection as compared with the 

 houses surrounded with the really dangerous native quarters. 



Segregation then we believe affords a very simple and practical 

 means of avoiding the danger of contagion. In villages in the 

 bush the process can be readily effected, and even in W. African 

 towns the difficulties are not really great. 



We may add solely that this mode of protection applies to 

 those conditions we have knowledge of in West Africa. We 

 cannot discuss its application to other conditions unknown to us. 



