Fig. 26.

Skeleton of a Snake.

sp, Spinous processes of the joints; r, ribs; q, quadrate bones, joining upper and lower jaws; e, front of the lower jaw, where there is an elastic band in the place of bone; b, ball end of joint, facing the tail; c, cup end of joint, facing the head.

We must not, however, imagine that the snake is at a disadvantage because he has lost so many parts which other reptiles possess. On the contrary, he has most probably lost them because he can do better without them. The transparent tough skin over his eye is a far better protection in narrow

rugged places, and among brakes and brambles, than a soft movable eyelid; and if he does not see as well as the crocodile, he has a most delicate organ of touch in his long, narrow, forked tongue, with which he is constantly feeling as he goes, touching now on one side, now on the other, each object he comes near, and drawing the tongue in at every moment to moisten it in a sheath at the back of his throat. A breast bone, moreover, would have been a decided hindrance to him, for he wants the free use of all his ribs; and as to the loss of his legs—in the place of four he has often more than two hundred. For all along his backbone, except just at the head and tail, a pair of ribs grow from each vertebra, being joined to it by a cup-and-ball joint (c and b, Fig. 26), and the muscles between them are so elastic that the ribs can be drawn out so that the body seems to swell, and then drawn back towards the tail. In doing this they strike the ground and the snake moves forwards, just as a centipede does on its hundred legs.

It is worth while to take our harmless Ringed Snake in your hand to feel this curious movement to and fro of the ribs, and to notice how the creature forces itself through your grasp. Moreover, you will learn at the same time one use of the broad single plates under the snake’s body (see Fig. 27), for they, like all the scales, are loose from the skin on the side towards the tail; and as they are fastened by muscles to the ends of the ribs, you will find that at each movement they stand up a little like tiles on a roof, and their edges coming against your hand help to drive the snake forward.

Another thing you will learn if the snake does not know you, and that is how strangely they hiss, often with their mouth closed, while their whole body seems to quiver. This is very puzzling at first, till you learn that one of their lungs has shrunk up, and the other is a very long and narrow bag stretching nearly the whole length of the snake’s stomach, and the hissing sound is made by drawing in and forcing out the air from this long bag.

Fig. 27.

Common Ringed Snake.[84]

Where the body is coiled the single under plates are seen.

Meanwhile, another way in which the snake will escape from your hold unless you grasp it tightly, is by wriggling in all directions, so that you do not know where to expect it next; for the whole of the joints of

Footnote 84. Natrix torquata.

its backbone are joined by a succession of cups-and-balls, the ball of one joint fitting into the cup in the one behind it. It is easy to see how such joints can move almost every way, since the ball can twist freely in the cup wherever the muscles pull it (except where checked by the spines on the top of the backbone), and can even turn so much to one side that the snake can coil itself round or tie itself into a knot.

A creature that can glide along so smoothly, twist about so freely round trees, through narrow openings and tangled brushwood, and even swim in the water, has no small advantage in life; and the snake can also coil itself up under a heap of dead leaves or in a hollow trunk of a tree for safety, or to watch for its prey when no animal would suspect it was near. But even the harmless snakes have something besides this, namely, the power of swallowing animals much broader and thicker than themselves. You will see on looking at the lizard’s skull (p. 103) that its bottom jaw is not joined at once to the top one, but there is a bone (q) between, which enables it to open its mouth wider than if the two jaws touched each other. Now this bone (q) in the snake’s jaw is so loosely hung that it moves very easily, and the lower jaw also stretches back far behind the upper one, so that when the snake brings the jaw forward it can open its mouth enormously wide. Nor is this all; it can actually stretch the bones of its jaws apart, for they have not their pieces all firmly fixed together. In the front of the mouth each jaw has elastic gristle in the place of bone, and the two halves of the jaw can thus be forced apart from each other, making room for a very large mouthful indeed.

Fig. 28.

The Boa Constrictor in the Forests of South America.

Now the snake’s teeth are all curved towards the back of his mouth, and they are never used for chewing or tearing, but only for holding and packing down its food. So when he seizes a creature too large to be easily swallowed, he fastens his front teeth into

it and then brings forward one side of his jaws. He then fixes the teeth of this side into the animal, and holds it fast while he brings forward the jaws on the other side, fixes these teeth, then loosens and brings forward the others, and so on. In this way he keeps his mouth stretched over the prey and gradually forces it down his elastic throat, moistening it well all the time with slime from two glands, one on each side of his mouth, and when it is swallowed he lies down and rests while the stomach digests its heavy load.

We see, then, that even harmless snakes have many advantages. Thus our ringed snake, feeding on mice and lizards, frogs and fish, wanders through the grass and bushes of warm sunny banks, feeling this side and that with his delicate forked tongue, and gliding so fast that the lizards and mice try in vain to escape; while in the water he seizes the frogs by their hind legs and jerks them into his mouth. He does not even always stop to kill his food, for a live frog has been known to jump out of a snake’s mouth as it yawned after its meal. So he lives through the summer, changing his skin several times by loosening it first at the lips, so that two flaps lie back over the head and neck, and then rubbing himself through moss, bush, or bramble, so that the skin is drawn off inside out like a glove, and the new skin appears underneath, fresh, hard, and bright, ready for use. Then in the warm season the mother lays her ten or twenty soft eggs in a mass of slime, and leaves them in some sunny spot, or under a heap of warm manure to hatch, and she herself wanders away, and when winter comes coils herself up in the trunk of some hollow tree, or under the hedge, to sleep till spring comes round again. Life does not always, however, flow so smoothly as this, for the snakes have their enemies; the fox and the hedgehog love to feed upon them, the buzzard and other birds of prey swoop down upon them from above, and the weasels attack them below; and this, perhaps, is partly the reason why the ringed snake generally keeps near the water, into which it can glide when danger threatens.

All snakes are not, however, so harmless as our little ringed snake. The Pythons of India and the Boas of America, though they have no poison in their teeth, can work terrible mischief with their powerful joints as they coil round even good-sized animals, such as an antelope or a wild boar, and crush them in their folds. Then it may be seen what a terrible weapon this flexible backbone is, as the muscles draw it tighter and tighter round the unfortunate animal, breaking its bones in pieces, till, when it is soft enough to be swallowed, the snake gradually forces it down its capacious mouth, moistening it with saliva as it goes. These large boas and pythons would, in fact, probably devastate whole countries if it were not that when they are young they are devoured by other animals, so that very few live to grow into dangerous marauders.

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

Footnote 85. Naja.

Footnote 86. Crotalus.

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.

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

Footnote 87. Naja tripudians.

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.

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