书城教材教辅科学读本(英文原版)(套装1-6册)
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第137章 第二册(54)

"Now just a word about the teeth of these cud- chewers. What do you remember about the sheep"s teeth, Norah?""It has no teeth at all in front of the upper jaw, only a thick, hard pad.""Right," said Fred. "Then, too, the back teeth have broad, flat crowns, and the lowerjaw moves from side to side, as well as up and down. These teeth arecalled grinders. They have to crush and grind up the food as in a mill.""Quite right," said Fred. "Now don"t forget, Norah, that the cow is exactly like the sheep in all these things."SUMMARY

The cow chews the cud. Like the sheep, it has a hard pad, instead of teeth, in the front of the upper jaw, and great broad teeth for grinding and chewing. It has four stomachs. It ?lls its paunch with grass, which it swallows mouthful by mouthful, without chewing it. The paunch passes the food into a second stomach, and this sends it up into the mouth, in cuds, to be chewed, after which it is swallowed again. The cow has a cloven hoof, exactly like that of the sheep. It touches the ground with only two toes in walking.

Lesson 25

Cast-Iron