Other snakes have taken a still more terrible way of killing their prey. There may be some chance of escape from a coiling snake, unless he already holds you with his teeth, but the poisonous Cobra[85] may strike before you know that you have startled him, and though the Rattlesnake[86] makes a sharp noise as he shakes the loose horny plates to call his mate or to alarm an enemy, yet when he means to strike his prey it is too late when the sound is heard to get out of reach of his fatal fangs. From the snake’s point of view, however, it is clearly an advantage to be able with one single stroke to paralyse its prey, so that it has only to wait for the poison to do its work, and then its meal is ready. Even our little viper (see p. 121), needs only to strike a mouse once, and then draws back as the poor victim springs up and falls and dies, soon to be packed down its destroyer’s throat. [Illustration: Fig. 29. The Cobra di Capello.[87]--(_From Gosse._) The mouth being closed, the poison fangs cannot be seen. The tongue is perfectly harmless.] Yet this terrible poison, which acts so speedily, is no special gift to the snake. It has only lately been discovered by M. Gautier that we, and probably all animals, have in our saliva some of the very poison with which the cobra kills its prey, only with us it is extremely diluted, and is useful in digesting our food. The cobra, however, has the poison, which no doubt exists in the slimy saliva of all snakes, specially concentrated and collected in two glands, one on each side of its jaw. From each of these glands (_g_) a small canal passes under the eye to the edge of the jaw (_c_), and opens immediately above a large curved fang (_f_). This fang is fastened to a bone in the cheek which moves easily, so that the poison teeth can be shut back and lie close against the gum when they are not wanted, and when they are wanted can be brought quickly down again. Though the fang looks round like ordinary teeth, it is really flattened out like a knife-blade, and then the edges are curved forwards so as to form a groove or, in some snakes, a closed tube, down which the poison can run to the point. [Illustration: Fig. 30. Jaw of a Rattlesnake. _ff._ Poison fangs; _g_, gland secreting poison; _c_, canal leading from gland to base of fang; _t_, harmless tongue; _s_, saliva glands. ] Now when the snake wishes to strike its prey it raises its head, brings down the fangs and drives them into the creature’s flesh, and at the same time certain muscles press upon the poison gland, so that the liquid poison is forced into the wounds. If, however, the fang was fixed to the canal, the snake’s weapon would be gone if the point were broken, so we find that the canal-opening lies just _above_ the tube of the tooth, and behind are six small reserve teeth, covered by a tender sheath skin, ready to grow up and take its place when wanted.