File:Rural sanitation in the tropics - being notes and observations in the Malay Archipelago, Panama and other lands (1915) (14746009256).jpg

Identifier: ruralsanitationi00watsrich (find matches)
Title: Rural sanitation in the tropics : being notes and observations in the Malay Archipelago, Panama and other lands
Year: 1915 (1910s)
Authors: Watson, Sir Malcolm
Subjects: Tropical medicine Rural health
Publisher: London : Murray
Contributing Library: University of California Libraries
Digitizing Sponsor: MSN

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to man. Thison the flat land was shown to be about 40 chains(half a mile) from the jungle breeding-pool. Thesemeasurements were made from jungle which generallyexisted as a menace to health only on one side of thecoolie lines, for, as a rule, there was a wide stretch ofopened land on other sides. In other words, themosquitoes on flat land came from only one direction. Our proposal for hill lands was to createa mosquito-free circle, into which, presumably,mosquitoes would pour from all points of thecompass. Would 40 chains be enough under thesecircumstances? It seemed to me to be well worthtrying less than 40 chains, for two reasons. Thefirst was that, on the hill land, mosquitoes wouldnot really fly in from all directions, for part of theboundary of the circle would be high dry land notbreeding mosquitoes. Mosquitoes would in realitybe breeding only in the ravines, and the mosquitoattack on the coolie lines might be likened to a seriesof columns (the number depending on the number of
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>-^:c»^f >- .^^r -rj. > xu Fig. 3.—BuKiT Ijok Estaie, Federated Malav States.Subsoil drainage to tap springs on the tide of a steep ravine. (fdci page 16. AREA OF DRAINAGE 17 ravines) advancing on a centre. The second reasonwas that 90 per cent, of the Anopheles caught on thelines of Seafield were A. maczilatus (vel willmori),and only 10 per cent. A. u7nbrosus. A. maculatusis a small and rather delicate mosquito, and it isreasonable to regard its malaria-carrying flight as lessthan that of A. timbrosus, the carrier on whom the flatland measurements were based. It was plain, too,that, purely as a business proposal, it was advisableto work from within outwards, for the area of thework and the expense of the work increases as thesquare of the radius. To double the radius of thecircle was at least to quadruple the expense. Takingall these things into consideration, I was content tobegin with about a 30-chain radius. By not drainingthe quarry ravine on Seafield Estate, we actua

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