exposed to the mid-day sun, but which had been several hours in shadow. So tenaciously had the reptile retained the heat it had then absorbed, that though the air now felt cold, the snake imparted _une chaleur très notable_ when he touched it. Many times, in taking up a lizard from a sunny rock in summer, it really has _brulé les doigts_.[49] The old fable about salamanders living in fire no doubt originates in the fact of reptiles loving heat as they do. Many pages might be filled with instances of this, and of their approaching fire to a suicidal extent. Equally strange is the degree of cold to which they can sometimes submit, and yet recover. But we must conclude that this is when they are overcome _gradually_, not suddenly, by it, and not exposed to the outer air so that the tissues would be injured. Dr. Carpenter mentions reptiles having been kept three years in an ice-house, and recovering on being gradually restored to warmth. Too recklessly acting upon this, I deposited my pet lizards in a small, shallow box containing moss, sand, and soft rubbish, and left them outside a window to hibernate. They buried themselves as deeply as they could go,—only a few inches, alas!—but a sudden and severe frost set in, and the poor little victims were frozen stiff at the bottom of their prison-house. It was in a bleak north-eastern aspect, and the sharp frost easily striking through the wood, that slight box must have proved a very different sort of nest to what they would have chosen on their native heath,—far down, and well protected from the icy winds. In a strong, deep box, or an earthenware jar, with sufficient earth and rubbish in it, they might have survived. In the Museum of Paris in 1875-76, sixteen rattlesnakes are said to have died of cold. The heating apparatus at the Jardin des Plantes is less effective than our own in London, where very few of the snakes have been known to suffer from lowered temperature. Snakes are abundantly supplied with oily fat; thick layers of it line their intestines in autumn, and this is gradually absorbed during their torpor. They therefore lose weight, and awake in an enfeebled condition, only gradually recovering their normal strength after some days. The power of endurance in serpents, and their independence of a large supply of oxygen, render them important agents in the economy of nature. In the swamps and morasses where malaria abounds, reptiles are most numerous. Many such places under canopies of pestilential vapours, swarm with insects, molluscs, worms, caterpillars, and the smaller reptiles on which snakes mostly feed. They are, therefore, the scavengers of such localities; they fulfil a great law by keeping up the balance of nature even to the extent of rendering certain countries habitable.