When we turn to human experience with diets rich in milk, some most interesting observations are met with. Certain regions have throughout history, produced vigorous and aggressive people. The Aryans and Mongols developed in the high pasture lands of Central Asia, where agriculture did not yield a return for labor, and where the care of flocks and herds formed the chief means of subsistence. Here in a climate characterized by extremes of heat and cold and of drought have originated the virile peoples who have become the possessors of the lands in every direction where the climate and soil were more favorable to an easy existence. Abstemious nomads, who knew no indulgence, and were every few years brought to face disaster through a scantier rainfall than usual, left their homes in wave after wave and dispossessed their neighbors in more favored lands. But in those more favorable circumstances where they came as conquerors, they not infrequently, in time degenerated into ease-loving agriculturists.