12 COMMON BRiTrsrr animals 



You will be able to see tliat puss has all these 

 parts. You can feel lier backbone running along 

 the top of her back and the bones in her tail, head, 

 and leo's, but it will be more difficult to feel the 

 girdles of bones ; however, you can feel 3^our own hip 

 and shoulder girdles. Just below your collar you 

 have a bone called the '' collar bone," one of the 

 bones of your shoulder girdle which helps to keep 

 the top of your chest extended. Now this bone 

 being absent from the cat^s shoulder girdle she is 

 consequently very narrow chested. A narrow chest 

 is an advantage to her, because she has a very small 

 surface to push through the air, and therefore can 

 move with greater speed. In the same way you try 

 to make yourself as narrow as you can if you want 

 to ride quickly on a bicycle. Puss can also squeeze 

 herself through surprisingly small apertures. You 

 know, it is said, that if a cat can get her head 

 through any hole she can get her body through it. 

 A protecting and movable cage of bones called the 

 ribs surrounds the lungs and heart. The arms and 

 legs of all backboned animals are constructed on 

 the same plan : one bone from the shoulder to the 

 elbow, two from the elbow to the wrist. A varying 

 number of bones form the wrist, to which are con- 

 nected the bones in the palm of the hand, and these 

 support the bones of the five fingers. Several 

 mammals walk, like the cat, on their toes, while 

 others, such as the bear and the monkey, walk 

 on the sole of the foot and palm of the hand, but 

 they do not all retain the five toes, as we shall see 

 later. 



