书城教材教辅科学读本(英文原版)(套装1-6册)
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第236章 第三册(61)

"We will next turn for a moment to the picture ofthe snake itself. The body, you see, is covered with scales, the one in front overlapping the one behind, so as to leave the hinder edge of all of them free.

"The scales are hard and horny, and those on the under part of the body are larger than the rest. These are joined to the lower ends of the ribs.

"Now, Norah, for your surprise. The snake moves about with these scales as if they were legs. The ribs can move in any direction. When the snake wishes to move, therefore, it advances its ribs. These carry with them the under scales. The scales take a firm hold of the ground or tree on which they rest, and the body is drawn forward with a gliding movement. Isn"t that all very wonderful, sister?"SUMMARY

Snakes have no limbs. They move on their ribs. They have many pairs of ribs. The skeleton is jointed with ball and socket joints. The body is covered with scales.

Lesson 20

How the Snake Feeds

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