In all these reptiles the poison-fangs are two in number, and are situated in the upper jaw. They are very sharp indeed, and are almost as brittle as glass. So while they are not in use they are folded back out of harm's way upon the roof of the mouth. But if by chance they should be broken, there are three or four other pairs lying ready for use behind them which will quickly grow forward to take their place. Generally there is a tiny hole just under the tip of the fang, which opens into a narrow passage running right through the center. But in some snakes there is only a groove outside the fang. In either case, however, the muscles which surround the poison-bag are arranged in such a way that as soon as the snake strikes its victim a drop of poison is squirted down each of the fangs, and so into the wound. VIPERS The only poisonous snake found in Europe is the viper, or adder. It is not by any means a large snake, for it is seldom more than twelve or fourteen inches long. It has a zigzag chain of black, lozenge-shaped markings all the way along its back. Vipers are generally found on heathy commons and moors, and are very fond of lying on a patch of bare, sandy ground, and enjoying the warmth of the sun. They never attempt to bite unless they are interfered with, but always try to crawl away, if alarmed, into a place of safety. Their poison is not strong enough to kill a man, unless he happens to be in a very bad state of health at the time when he is bitten; but it would be quite sufficient to cause the bitten limb to swell up to double its size, and to lead to a great deal of suffering and sickness. COBRAS Far more deadly is the bite of the cobra, which is found plentifully in India. Any one who is bitten by this formidable snake is almost sure to die within two or three hours. The upper part of a cobra's neck is widened out into what is called the hood, which can be spread out or folded up at will by the action of the ribs. On the upper part of this hood is a dark mark, which looks almost exactly like a pair of spectacles. When a cobra is about to strike it always raises its head and neck and spreads this hood before darting at its foe. In many parts of India cobras are caught and tamed by men who are called snake-charmers, and who sometimes capture them by playing an odd tune upon a sort of wooden pipe. This music seems to fascinate the snake, which comes out of its hole, rears up its head and neck, and begins to sway slowly from side to side. Then, still playing, the charmer moves his right hand very slowly indeed until it is just behind the snake's head, when he suddenly grasps the reptile round the neck. It is now, of course, quite helpless, and is quickly transferred to his bag. Many charmers carry cobras about with them, which they handle quite freely. But in these cases the poison fangs have been carefully extracted, so as to render the reptiles harmless.