24 NATUBAL HISTOKT. 



State the difference between them. Give the difference between the 

 two classes of warm-blooded Vertebrates. What is the derivation of 

 oviparous and viviparous ? Name the sub-classes of the Mammals. 

 What is said of the first class ? What of the second ? Of the third? 

 or the fourth ? Of the fifth ? 



CHAPTER II. 



25. Man is said to stand at the head of the animal 

 kingdom. It is well that you should understand pre^ 

 cisely what this means. We may consider every animal 

 as a set of machinery, which is worked by means of the 

 nervous system. In some animals this machinery is very 

 simple, as in those which are nearly all stomach (§ 19). 

 In others it is complicated. In man it is more so than 

 in any other animal. For example, take that part of the 

 machinery that is used in motion. Compare man with 

 any animal in this respect. How many more motions he 

 can make with his feet than a horse, or an ox, or a dog. 

 The dog can walk, run, jump, and paw. To say nothing 

 of other motions, observe in contrast the extreme varie- 

 ties of motion of which the feet of man are capable in 

 dancing. 



26. There is no part of the machinery of the body in 

 which man is so manifestly superior to other animals as 

 in that of the hand. The variety of things that this ma- 

 chinery can do is so great, that you can get an adequate 

 idea of it only by watching the motions of the hand in 

 all the different kinds of work and play in which it en- 

 gages.* 



27. Look now at the instrument or machine itself 

 How simple it appears ! You have merely a thumb and 



* This and many other of the points in this chapter are quite fully 

 treated in my " Child's Book of Nature," and " First Book in Physi- 

 ology." 



