MOVEMENTS. ] 



PHYSIOLOGY. 



21 



one side of the head is almost exactly like the other. 

 One side of the vertebral column is exactly like the 

 other — as are also the two halves of the brain and the 

 two halves of the spinal cord. ^ . , 



In fact, if you were to cut your rabbit in half from 

 his nose to his tail, you would find that except for 

 his alimentary canal, his heart, and his liver, one half 

 was almost exactly the counterpart of the other. 



Such is the structure of a rabbit, and your own 

 body, in all the points I have mentioned, is made up 

 exactly in the same way. 



WHAT TAKES PLACE WHEN WE MOVE. § III. 



13. Let us now go back to the question. How is it 

 that we can move about as we do ? And first 

 of all let us take one particular movement and see if 

 we can understand that. 



• For instance, you can bend your arm. You 

 know that when your arm is lying flat on the table, 

 you can, if you like, bend the lower part of your arm 

 (the fore-arm as it is called, reaching from the elbow to 

 the hand) on the upper arm until your fingers touch 

 your shoulder. How do you manage to do that ? 



Look at the bones of the arm in a skeleton. 

 (Frontispiece ; also Fig. 3.) You will see that in the 

 upper arm there is one rather large bone {H) reaching 

 from the shoulder to the elbow, while in the fore-arm 

 there are two, one (Z7). being wiler and stouter than 

 the other {Rd) at the elbow, but smaller and more 

 slender at the wrist The bone in the upper arm is 

 called the humerus ; the bone in the fore-arm, which 

 is stoutest at the elbow, is called the ulna \ the one 



