In these cells the animal is able to store up water. When it has the opportunity of drinking, it not only quenches its thirst, but fills up all these cells as well. In this way it can store up quite a gallon and a half of liquid. Then, when it grows thirsty, and cannot find a pool or a stream, all that it has to do is to open one or two of the cells and allow the contents to flow out, and so on from time to time until the whole supply is exhausted.
In this way a camel can easily go for five or six days without requiring to drink, even when marching under the burning sun of the desert.
Two kinds of camels are known, neither of which is now found in a wild state.
Arabian Camel
The first of these is the Arabian camel, which only has one hump on its back, and is so well known that there is no need to describe it. It is very largely used in many parts of Africa and Asia as a beast of both draught and burden. Camels for riding upon, however, are generally called dromedaries, and may be regarded as a separate breed, just as hunters are a separate breed from cart-horses. And while they will travel with a rider upon their backs at a pace of eight or nine miles an hour, an ordinary camel with a load upon its back will scarcely cover a third of that distance in the same time.
This camel is a bad-tempered animal. It gets very cross when it is made to kneel down to be loaded, and crosser still when it has to kneel again in the evening for its burden to be removed, and all day it goes grunting and snarling and groaning along, ready to bite any one who may come near it. And it is so stupid that if it wanders off the path for a yard or two, in order to nibble at a tempting patch of herbage, it goes straight on in the new direction, without ever thinking of turning back in order to regain the road.
Besides being used for riding and for carrying loads, the camel is valuable on account of its flesh and also of its milk, while its hair is woven into a kind of coarse cloth.
Bactrian Camel
This camel, which comes from Central Asia, has two humps on its back instead of one. It is not quite so tall as the Arabian animal, and is more stoutly and strongly built, while its hair is much longer and more shaggy. For these reasons it is very useful in rocky and hilly country, for it can scramble about for hours on steep and stony ground without getting tired, while its thick coat protects it from the cold.
Llamas