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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ed by a suctiondredger which, employed in deepening the Canal, hadpoured salt water and silt into an area of fresh-waterjungle. The immediate effect of the salt water wasto kill off the trees and all vegetation. The silt wasdeposited, and raised the land; while the salt water,more or less diluted from the fresh water in thejungle, ran off by a drain at the end of which we hadlanded. The dead and dying timber produced bythis hydraulicing apparently provided abundantfood for Anopheles albimanus (A. tarsimaailatus,a sub-species), and also for the fish, which swarmedat the end of the exit drain. I have never seen agreater number of fish together. They varied insize from 3 feet long to tiny sprats. They jumped,and splashed, and dashed up the drain, only to bedriven back by its strong current. In every eddyand corner there was a black mass of the smallerfish. A number of tortoises were also seen on thebanks, and some in the water. Evidently the end ofthe drain was a splendid feeding ground.
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BREEDING-PLACES OF ANOPHELES 139 Walking- up it for about 300 yards, with beautifulfresh green jungle on our left, we suddenly came toa drain across our course, on the other side of whichthe trees were dead and leafless—a picture of desola-tion. Anopheles larvae were easily found in thebrown dead grass at the side of the lateral drains,although I was told they were not nearly so numerousas they had been. I was struck with the number ofsmall fish in the water, and at one place where thelateral drain narrowed to a passage of about a footwide and 2 inches deep, I estimated the fish werepassing- at the rate of four or five a second. Yetwithin a yard of this constriction we got from threeto twelve Anopheles larvae at each dip among thedead grass. There was practically no current in theselateral drains. The protection afl^orded by the grassdid not seem sufficient to prevent fish with anyenterprise securing the larvae had they been soinclined. Many of the fish were as small as themillions.

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