MALARIA EXPEDITION TO NIGERIA 249 
house — and this is a serious consideration in climates such as that of West Africa — 
the habits of the European in that country expose him repeatedly to the bites of 
Anopheles at times of the day when it would be impossible for him to be inside a 
mosquito-proof house. The offices of the government and the warehouses and shops 
of the traders it would be impossible to protect in this way, while innumerable people 
continually enter and leave — and here many Anopheles are often very troublesome. 
Similarly, work being done for the day, it is a common practice with all the 
Europeans to sit out after sunset in their verandahs, or in the open, enjoying the 
cool of the evening — exposed to the attack of mosquitoes, which become active at 
this time of day. 
Destruction of the Insect 
(a) Of adults. This evidently can be executed to a very small extent only, 
and is not to be considered as of any material help to prevention. The ease with 
which they can be caught is, however, noteworthy— native boys soon recognised the 
difference between Anopheles and Culex, and brought us often as many as fifty or more 
of the former every day, either in test tubes or even in bottles — large numbers in each. 
(b) Of larvae — and the extirpation of breeding places of Anopheles. This pre- 
sents a very large field of operations against the mosquito. The extermination of the 
definitive host will naturally occasion the destruction of the malarial parasite. 
The chief result of the previous expedition to West Africa (Sierra Leone) was 
to establish the fact that breeding-places of Anopheles are often easy of destruction or 
of prevention, and that this procedure would, to a large extent, prevent malarial fever 
in districts where it was thoroughly carried out. Two courses were suggested. 
1 Efficient drainage — and the construction of proper roads — and the filling 
up of pools and puddles of water to prevent the formation of breeding-places. 
2 The use of 'cuhcicides,' to be added to existing breeding-places regularly and 
intelligently, to kill larvae present, and to prevent future use of the water for the 
purpose of breeding. 
Although the first method was suggested as the only really efficient measure, 
the second was offered as a temporary measure until the financial condition of the 
colony would permit of the expenditure necessary for the carrying out of the first, and 
also for adoption in those rarer circumstances where the more efficient method could 
not be applied. 
The material changes which have been brought about in the prevalence of 
malarial fever in some towns in tropical and sub-tropical countries, especially in India 
and Southern Africa, by the introduction of a good drainage scheme, were previously 
described as the results of general sanitary improvement, and it was decidedly established, 
before the part played by mosquitoes in malarial infection was even hinted at, that the 
adoption of good drainage methods was often immediately followed by a more or less 
