2 5 o THOMPSON YATES LABORATORIES REPORT 
complete disappearance of malarial fever in the district. Now, of course, such 
improvement must be ascribed to the destruction of the breeding-places of Anopheles. 
As has already been shewn in previous chapters of this report, the conditions 
met with in Nigeria are extremely varied. Districts may be very roughly classified, 
according to the nature of their more common breeding-places for Anopheles, as 
follows : — 
(a) Those in which native dug-out canoes, and occasionally shallow sur- 
face puddles are usual — for example, at Old Calabar, Bonny, 
Opobo, Okrika, etc. etc. 
(b) Those with shallow surface puddles only — the areas of many of the 
factories of the various trading companies. 
(V) Those having mud and clay pits, wells and pools, and few surface 
puddles. — Abonnema, Egwanga, Okoyong, etc. 
(d) Those with ' made ' roads, having ditches at the side and small hill 
streams — Lokoja. 
(e) The neighbourhood of fresh-water marsh districts in cultivated and 
occasionally uncultivated areas. — Lokoja, vice-consulate at 
Opobo. 
(/) Towns on the banks of rivers which fall considerably during the dry 
season. — Agberi, Asaba, and many others. 
It must be distinctly understood that these do not include all the breeding- 
places of Anopheles, and we are of opinion that it would be extremely difficult, even in 
a small district, to indicate all the collections of water which might from time to time 
serve as breeding-places. For we urge that the destruction of the usual breeding- 
places of Anopheles would be followed by the adoption of any piece of water that might 
be presented if of sufficient duration, and that at length the various unlimited breeding- 
places usually frequented by Culex would be resorted to. Such a condition, however, 
would be rendered difficult under the circumstances of modern European domestic 
life. 
In almost all of the classes into which districts have been placed according to 
the conditions under which Anopheles breed, an efficient surface drainage is more or less 
applicable. Many of the compounds of the trading companies' factories (b) are roughly 
kept, and present irregular unlevelled surfaces permitting the formation of numerous 
shallow puddles in the rainy season. The careful construction of a few gutters and 
ditches would obviate the evil, and thus destroy almost the whole of Anopheles breed- 
ing-places in the immediate vicinity of the factories — which often are the only source 
of Anopheles. 
The numerous clay and mud pits of districts (c) which occur in almost every 
native town outside the mangrove swamp region, would be difficult to treat by drain- 
age. From them the natives obtain mud or clay wherewith to build their huts and 
