The Camel, next to the Horse, is the most useful beast of burthen. The Arabs greatly prize these creatures, and from their power of carrying a supply of water in their stomach, they are very useful in crossing the desert; their hoofs are also spread out so as to enable them better to walk on the soft and yielding sand; there are two kinds of Camel, the Bactrian, with two humps, and the Arabian Camel with but one. The Dromedary is a small agile breed of the Arabian Camel, celebrated for its swiftness. * * * * * 6. The PACHYDERMATA or thick-skinned animals (fig.64) include the Elephant, Rhinoceros, Horse, Ass, and its varieties; Hog, Tapir, Hippopotamus, &c.; these have many of them a single solid hoof on each foot, as in the Horse and Ass tribe, others have separate toes clothed with a hoof, as in the Elephant. In nearly all the Pachydermata there is a prolongation of the nose or upper lip, the Horse even has some power of prehension in this part; the Rhinoceros is able to bring the upper lip into so fine a point as to pick up a crumb, and in the Tapir there is a considerable prolongation of the nose, while the Elephant has this part developed into a complete prehensile organ. The Elephant, Rhinoceros, and Hog are fond of wallowing in the mud, with which they completely besmear themselves, and seem to derive great satisfaction therefrom. There are two kinds of Elephants, the Asiatic, or Indian, and the African, the chief distinction between them is the size of the ear, that of the African Elephant being of very great size; there is a very young specimen of this kind in the British Museum, but a full-grown African Elephant has never been brought to England. The Elephant is furnished with a pair of enormous tusks proceeding from the upper jaw, these are composed of solid ivory, and often weigh nearly a hundred pounds each; with the trunk, the Elephant is able to gather food in the form of grass and herbage, and put it into its mouth, it can also draw up a considerable quantity of water, and this being poured down its throat from the trunk, constitutes its usual mode of eating and drinking, as the neck is too short for the animal to reach the ground except by the trunk. The Indian Elephant is much used as a beast of burthen, and for various other purposes; they are very docile and sagacious. [Illustration: FIG. 64.--PACHYDERMATA. 1, Elephant (Elephas Indicus); 2, Rhinoceros (Rhinoceros unicornis); 3, Hippopotamus (Hippopotamus amphibius); 4, Wild Boar (Sus scrofa).]