Among the Arabs, everything concurs to give power to the development of the natural man. Nervous, hardy, sober, though occasionally displaying a vigorous appetite, their eyesight is keen and piercing. They boast that they can distinguish a man from a woman when two to three leagues distant, and a flock of camels from a flock of sheep at double that distance. Nor is this mere bragging. The extent and clearness of their vision arise, as in the case of our sailors, from the incessant habit of looking far ahead over an immense and objectless space. And, accustomed as they are to scenes and objects always the same and which encircle them within narrow limits, it would be strange if they did not recognize them under almost any circumstances. Nevertheless, diseases of the eye are very common. The refraction of the sun's rays, the dust and perspiration cause numerous misadventures, such as ophthalmia and leucoma, and blind and one-eyed men are numerous in many parts of the desert—for instance, among the Beni-Mzab, at El Ghrassoul, Ouargla, and Gourara. The dweller in the desert, in infancy and youth, has beautiful white, even teeth; but the use of dates as his habitual and almost exclusive diet spoils them as he advances in years. When a tooth is entirely decayed, he is compelled to have recourse to the armourer or farrier, who is privileged to torture his patient, to break his jaw with his pincers, and tear away the gums together with the tooth that was troubling him. The genuine chief, the real great lord, rarely leaves the saddle, and very seldom goes on foot, though he wears both boots and shoes. The common Arab, however, is an indefatigable walker, and in the course of a day will get over an incredible distance. His ordinary pace is what the French call the _pas gymnastique_ [which is quicker than the English "double"], and what he himself calls a dog-trot. On flat ground, he generally takes off his shoes, if he happens to have any, partly that he may walk faster and more comfortably, and partly that he may not wear them out. Consequently, his foot is like that of antique statues, broad and flat, and with the toes wide apart. He is never troubled with corns, and more than once Christians, who have insinuated themselves into caravans, have been detected by this infallible sign and expelled. The sole of the foot acquires such hardness, that neither sand nor stones affect it, and a thorn sometimes penetrates to the depth of several lines without being felt. In the desert, properly so called, however, the sand during the great heat of summer is so burning hot that it is impossible to walk upon it with naked feet. Even the horses are obliged to be shod, or their feet would become painful and diseased. The dread of being bitten by the _lefâ_, a viper whose venom is fatal, also compels the Arabs themselves to wear buskins rising above the ankle.