书城教材教辅科学读本(英文原版)(套装1-6册)
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第239章 第三册(64)

"Try to imagine a snake in the act of swallowingits 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.

Lesson 21

Mercury