It was a great step in advance when animals from which the horse, cow, goat, sheep and camel have descended, were domesticated. With these, man was able to invade grassy plains. Their animals converted coarse herbage into milk, a human food of very excellent quality and which was never failing in its supply. Solicitude for his animals, and the problems of protecting and caring for them, stimulated mental activity and cultivated in him some of the highest attributes of human nature. But his superior nutrition assured him health and vigor, and made him capable of successfully contending with his neighbors of fertile valleys who attempted to practice agriculture, or who subsisted by hunting, and he dispossessed them, at will, of their land and property. He migrated from his home in the pasture lands only at intervals when drought threatened to destroy his flocks and herds, but when he left his home it was always as a conqueror. The Jews, moving into Palestine; the Aryan hoards who migrated westward and peopled Europe, and the Mongols, who under Ghengis Khan and his successors dispossessed their neighboring tribes, were all pastoral peoples. Their descendants of to-day live as did their ancestors of thousands of years ago, the lives of pastoral nomads on the pasture lands of Asia, and are nourished for the most part on sour milk. The Cossacks who have for so long formed the backbone of the Russian army are from this class, and the ancestors of the Turks were, and indeed most of the rural Turkish population of to-day are pastoral in their habits, and are living examples of the fine physical development and freedom from defects, which are the inheritance of sour milk drinkers generally. The sourness of the milk which they use as food is, it should be stated, a matter of secondary importance. Prompt souring is the most effective means at their disposal for preserving milk in a wholesome condition.