This includes the Serpents, Boas, and Pythons. These creatures are peculiar from their long and flexible form, and the absence of legs. They move by a sinuous winding action, and when about to seize their prey, make a sudden dart with great rapidity. They are covered with regular scales, and mottled with different colours; some, as the Adder and Rattle-snake, are very venomous, the poison is contained in small glands connected with the poison-fangs, which are two long pointed teeth, having a groove or small canal leading from the side of the tooth to the poison-bag, upon which, when they bite, they press, and inject the poison into the wound while the tooth is in the flesh. These poison-fangs lie flat down when the creature is not excited, but are drawn up by muscles, when they are about to spring on anything. It is a common mistake to think that Serpents have a "sting," arising from their having a thin, long forked tongue, which they protrude and retract with great rapidity, and which has been mistaken for a sting; the greater number of Snakes are not at all venomous. Serpents have no teeth fit for eating with, but they are used to hold their prey, while they swallow it, and they serve admirably for this purpose, as each tooth turns backwards. These creatures have mouths and throats capable of enormous distension (the lower jaw not being fixed to the upper one), so that they can swallow their food whole, which they always do; a Frog or Toad is often swallowed by the common Snake, which is quite disfigured by it when in its stomach. The Pythons and Boas (fig. 48) are the largest of this class, they kill their prey by coiling round it, and gradually tightening their folds till it is suffocated and almost crushed, when it is swallowed; these great creatures will grow to the length of 30 or 40 feet, and are capable of swallowing considerable quadrupeds, as Hares, Goats, Deer, &c.; after having their food, they lie torpid for several days. All Serpents lay eggs, and the Pythons coil themselves round upon their eggs to protect them; the Boa-constrictors are inhabitants of America, the Pythons of the Old World. 3. SAURIA (Lizards).