This then is the origin of the "Master Instinct," hunger. When we consider the various emotions growing from the force of this vital urge, as developed by adaptation to an ever-changing environment, we are able to realize fully why it bulks so large in moulding and shaping the destiny of the race. All psychologists are agreed in classing under the nutritive instinct such activities as acquisition, storing and hoarding. During a period variously estimated as a quarter of a million to two million years, man and his animal antecedents responded to the hunger instinct, in the manner and by the same methods as did the various jungle animals. He secured his prey by capture, or killed it wherever found, the one condition being his power to get and to hold. Later tribal organization arose, and food and shelter were held in common. But since the folk-ways commended raiding and looting between alien tribes, here was presented an alluring chance to secure both booty and glory to men trained in the "get and hold" process of acquiring. For thousands of years life itself depended upon this unerring exercise. It was during the period outlined that man developed his big brain (cerebrum) involving the central nervous system. Furthermore, it was developed by, and trained to, these particular reactions. The far-reaching control of the mind must be remembered, as upon this through his racial heritage must be based his conflicting impulses. These must be reckoned with in our conclusions with regard to present-day behavior, economic or otherwise. During the last thirty years, psychological laboratories, aided by physiology, through oft-repeated experiments conducted with newly-invented weighing and measuring instruments of marvelous accuracy, have put us in possession of an array of facts unknown to students of earlier periods, who sought the "why and the how" of man's erratic actions as a social animal. It is constantly being demonstrated that under given conditions, moved by appropriate stimuli, the human animal inevitably and surely reacts the same as does inorganic matter. If we understand "intelligence" to be the "capacity to respond to new conditions," we can measurably see and at least partly understand the constant inter-play of heredity and environment. Between these there is no antagonism. The sum of life experiences consists solely in the adjustments required to enable the sentient organism--man or beast--to live. How readily a "throw-back" to earlier and cruder life may be brought about under favorable conditions, is shown by the methods and virulence of combat during the vicious massacre in the war just ended. Can the conclusion be evaded that individually and collectively we constantly teeter on the brink of a precipice? If we fall it spells crime or misfortune, or both.