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. 
