Some Remarks on Malaria Prophylaxis

phylaxis, and especially those of the Royal Society Reports to the Malaria Committee, 1 have been struck by the absolute absence ol mention of" wind" as a very serious factor to contend with. Observations have been made on the flight ol the mosquito aud the utmost distance allowed is half mile. As several observers agree to this distance according to the observations they have made, the conclusion to be drawn is that the observations were carried out in a comparatively undisturbed atmosphere. Now in a great many Cantonments where malaria is prevalent, there is generally a breeze of greater or less strength most evenings with the result that mosquitoes must be able to travel a distance far greater than half mile. This point, I was able to satisfy myself on, in the Malakand. In the Fort there, during the malaria season in the Swat Valley, I have been able to catch anopheles in very fair numbers. Having examined the ground thoroughly on all sides, there was every reason to suppose that breeding did not take place in the near Vicinity. The only conclusion to come to was, that they had come up from the rice-fields and swamps in the Swat Valley, a distance of about three miles as the crow flies. Mosquitoes breeding in abundance I have found in multitudinous spots in this valley. It is the rarest thing for the breeze to fail at nights, and the direction is always from the valley to the Malakand. Taking this point into consideration, how futile it seems to try and destroy larvae with kerosene oil in a district ^here cultivation spreads for some distance on the windward side of the place that requires protection. The utmost that can be expected from such operations is a slight reduction in the quantities of mosquitoes, but is a reduction, only, sufficient ? Certainly not, judging by the slight reduction in the malaria incidence that took place after the operations in Mian Mir. However, even though a slight reduction does take place, I would not have the war against larvae to cease but continued actively in the cold weather and at such times when irrigation is not extensive. Canal cuts, on the windward side of a canton-