PROGRESSION OF ANIMALS, ii.-iii. 



something else is only moved accidentally, for what 

 is carried by something else is regarded not as mov- 

 ing itself but as being moved by something else. 



III. These points having been decided, let us 

 proceed to the considerations which follow from 

 them. Of the animals, then, which change their local 

 position, some do so with their whole body at the 

 same time, for instance those which jump ; others 

 move part by part, for example those that walk. 

 In both these changes the animal that moves makes 

 its change of position by pressing against that which 

 is beneath it ; and so, if the latter slips away too 

 quickly to allow that which is setting itself in motion 

 upon it to press against it, or if it offers no resistance 

 at all to that which is moving, the animal cannot move 

 itself at all upon it. For that which jumps performs 

 that movement by pressing both on its own upper 

 part and on that which is beneath its feet ; for the 

 parts in a way lean upon one another at their joints, 

 and, in general, that which presses leans on that 

 which is pressed. Hence athletes jump farther if 

 they have the weights in their hands than if they 

 have not," and runners run faster if they swing their 

 arms ^ ; for in the extension of the arms there is a 

 kind of leaning upon the hands and wrists. Now that 

 which moves always makes its change of place by the 

 employment of at least two organic parts, one as it 

 were compressing and the other being compressed. 

 For the part which remains still is compressed by 



Athletic Sports and Festivals, pp. 298 if., who proves by- 

 experiment the truth of the statement made in the present 

 passage. 



'' On the importance attached by the Greeks to arm- 

 action in running, especially in short races, cf. N. Gardiner, 

 op. cit. p. 282. 



489 



