War and famine, whether the famine has been produced by drought, insect pests, floods, tornadoes, earthquakes, freezes, snows, etc., have frequently deprived whole populations of food for extended periods, so that they have been forced to fast. In many of these instances they have had limited food supplies, but in others no food has been available for long periods. The ability of man to fast, even for long periods, proves to be, as with the lower animals, an important means of survival under such circumstances. Such prolonged periods of deprivation were much more frequent in past ages than today, when rapid transportation and modern means of communication make it possible to get food to people in famine districts in a very short time.