英文科學(xué)讀本 第三冊(cè)·Lesson 20 How the Snake Feeds

Lesson 20 How the Snake Feeds

Shall we have another look at the snakes, Norah? asked Fred.

Oh do, please, said his sister. "I'll go and bring your new book."

Well then, began Fred, as soon as they were seated, "suppose we talk about their habits of feeding. Snakes are as curious in their feeding as in everything else."

They all live on animals. Some of the smaller snakes prey upon frogs, mice, rabbits, and other creatures they find on the ground. Some live almost entirely in the trees, and feed upon squirrels, birds, and even monkeys. But they all feed in one way.

Animals like the cat, the dog, and the mole also live on flesh.

How could we find this out for ourselves, if we did not know?

We should examine the teeth of the animals, said Norah. "That would tell us."

Ah, but the strangest part of the snake is, said Fred, "that it has no long canine teeth for tearing flesh, and no sharp jagged teeth for cutting it through. The flesh-eaters have, but the snake has not. Snakes are not flesh-eaters."

Why, I thought you just now told me, said Norah, "that all snakes feed on flesh."

Yes, dear, said Fred, "so I did. But snakes do not eat their prey as the flesh-eaters do. They swallow them whole."

Oh, how very dreadful, said Norah.

Let us look again at the skeleton of the snake, said Fred. "The teeth, you see, in both jaws are small and sharp-pointed, and they all bend backwards towards the throat."

Such teeth would be useless for tearing flesh or for chewing purposes. They are meant to hold the victim fast between the jaws while it is being drawn down the throat.

But the most wonderful thing of all seems to be, that even the bones of the snake are made to help in the work of swallowing. Every bone of the head—the upper jaw as well as the lower—is movable. They are all jointed by ball-and-socket joints, and can be easily pushed out of their places. You know that the separate bones of the back, and the ribs which join them, are all arranged on the same plan, with ball-and-socket joints.

Try to imagine a snake in the act of swallowing its prey. It takes a firm hold with the pointed teeth of one jaw, and draws its victim in, and then proceeds to take a fresh hold with the teeth of the other jaw. This action is repeated again and again, till the animal disappears down its throat, the bones of head, mouth, and throat all the time moving out of their sockets to make room.

After the animal is swallowed, the ribs and the bones of the back move aside in the same way, to give more space for it in the stomach. Even the overlapping outer scales of the body do their part. They readily slip aside to make more room, as the body of the snake expands with its meal.

It is clear therefore that the snake swallows its prey whole, because every part of its body was meant for this kind of feeding.

SUMMARY

The snake's teeth are small and sharp-pointed; they all bend backwards; they hold the victim as it is being swallowed. The snake swallows its prey whole, because every part of its body is made for this kind of feeding.