What is a camel's hump for?

Camel's hump - a camel uses its hump as a portable storehouse of fat from which to draw nourishment when food is scarce. A chemical process enables the camel to covert some of this fat into water, an advantage which enables it to survive for up to 17 days in the desert without drinking. The Arabian camel or dromedary, found in Arab countries of the Mediterrian, has only one hump. But the Bactrian camel of western Asia has two, giving it greater powers of endurance. A camel has a especial way of running called "pacing", which looks like an slow run and saves energy. Yet another advantage which enables the camel to survive in regions where food is scarce is its ability to eat twigs and thorny plants which other animals would not touch.As is the case with all animals, including the human beings, the greater part of a camel's body weight consists of water. But, unlike us, this "ship of the desert" can lose up to a quarter of the water through dehydration and live to make another journey. When it does get a chance to replenish supplies, it can put all that weight back in 10 minutes by drinking 25 gallons of water at a time. The Bactrian is slower than the Arabian, but has more stamina.