REPORT OF THE LIVERPOOL MALARIA 
EXPEDITION TO THE GAMBIA 
I. PRELIMINARY 
DURING the past two years a great deal of energy has been displayed in many 
parts of the world to put to some practical use the great discovery of the 
definitive host of the malaria parasite. The knowledge that the mosquito 
is responsible for the transmission of malaria has immensely increased the possibility 
of combating this disease by prophylactic measures. The measures which have been 
recommended by various investigators naturally group themselves under two heads — 
1. Destruction of the parasite in its intermediary host, man. 
2. The prevention of the transference of the parasite from one host to 
the other, viz., from man to mosquito, or mosquito to man. 
Under the latter group many methods have been advocated, and much 
literature has accumulated during the last three or four years. The modes of attack 
have centred round the vulnerable stage in the life cycle of parasites in general, viz.? 
the transference from one host to another ; thus in the case of the malaria parasite the 
points aimed at in this stage are — 
I. Destruction of the definitive host, the mosquito. 
1. The prevention of infection of the mosquito. 
3. The prevention of inoculation of man by the mosquito. 
It was hoped in the early stages of the work of investigation on the mosquito 
cycle of the malaria parasite that it would be a matter of comparatively little difficulty 
to destroy the parasite in this stage of its history by means of the destruction of the 
mosquito carrying them, especially as only one genus of the Culicidae {Anopheles) was 
implicated. Major Ross, in India, and other investigators had pointed out the broad 
fact that the genus Anopheles required, as a rule, breeding-places of a rather special 
character for their propagation, very shallow surface pools of sufficient depth to last 
over a week. By the prevention or treatment of these pools it was thought that the 
mosquitoes could be done away with. Maps were made marking out the distribution 
of such breeding places throughout certain districts with this object in view. Later 
on it was shown that certain members at least, if not the whole genus Anopheles, did 
not necessarily require such specialized breeding places, for if from any cause they 
were absent these mosquitoes would breed in any collection of water, just as the genus 
Culex does. 
