Abstract

From those very early days when prehistoric man gave up his nomadic and predatory habits and began to raise crops and tend cattle the struggle between nature and man must have com- menced in right earnest, man upsetting the normal conditions prevailing in the universe, and nature asserting herself every time to re-establish her supremacy. Gradually, through centuries of civiliza- tion, as this protracted struggle continued, one of the most important changes effected has been a pronounced re-adjustment of the relations that originally existed between man and the lower forms of lifc. Under the numerous artificial conditions brought about by human agency. what is known as the "balance of life" in nature is constantly upset especially among the lower animals like insects and one of the various resulting phenomena which frequently happens is an abnormal increase in the number of some lower forms of life which affect men-in other words, there is an outbreak of pests. Man has, of course, recognised this self-inflicted but inevitable evil through past decades and in all countries.

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