According to the accounts of travellers, the Cerastes is much more irritable than the cobra, and is very apt to strike at any object which may disturb it. Therefore, whenever a horseman passes along the usual route, his steed is very likely to disturb a Cerastes lying in the path, and to be liable to the attack of the irritated reptile. Horses are instinctively aware of the presence of the snake, and mostly perceive it in time to avoid its stroke. Its small dimensions, the snake rarely exceeding two feet in length, enable it to conceal itself in a very small hollow, and its brownish-white colour, diversified with darker spots, causes it to harmonize so thoroughly with the loose sand in which it lies buried, that, even when it is pointed out, an unpractised eye does not readily perceive it. Even the cobra is scarcely so dreaded as this little snake, whose bite is so deadly, and whose habits are such as to cause travellers considerable risk of being bitten. The head of the Viper affords a very good example of the venomous apparatus of the poisonous serpents, and is well worthy of description. The poison fangs or teeth lie on the sides of the upper jaw, folded back, and almost undistinguishable until lifted with a needle. They are singularly fine and delicate, hardly larger than a lady's needle, and are covered almost to their tips with a muscular envelope, through which the points just peer. The poison bags or glands, and the reservoir in which the venom is stored, are found at the back and sides of the head, and give to the venomous serpents that peculiar width of head which is so unfailing a characteristic. On examining carefully the poison fangs, the structure by which the venom is injected into the wound will be easily understood. Under a magnifying glass they will be seen to be hollow, thus affording a passage for the poison. When the creature draws back its head and opens its mouth to strike, the deadly fangs spring up with their points ready for action, and fully charged with their poisonous distillment. [Illustration: viper] THE VIPER, OR EPHEH. The Sand-Viper, or Toxicoa--Its appearance and habits--Adder's poison--The Cockatrice, or Tsepha--The Yellow Viper--Ancient ideas concerning the Cockatrice--Power of its venom. We now come to the species of snake which cannot be identified with any certainty, and will first take the word _epheh_. Mr. Tristram believes that he has identified the Epheh of the Old Testament with the Sand-Viper, or Toxicoa. This reptile, though very small, and scarcely exceeding a foot in length, is a dangerous one, but its bite is not so deadly as that of the cobra or cerastes. It is variable in colour, and has angular white streaks on its body, with a row of whitish spots along the back. The top of the head is dark, and variegated with arrow-shaped white marks.