PARTS OF ANIMALS, IV. x. 



bility of its coming together into one solid piece, 

 whereas the reverse order of events would be im- 

 possible. Also, it is possible to use them " singly, or 

 two at a time, or in various ways. Again, the joints 

 of the fingers are well constructed for taking hold 

 of things and for exerting pressure. One finger is 

 placed sideways : this is short and thick, not long 

 like the others. It would be as impossible to get 

 a hold if this Mere not placed sideways as if no hand 

 were there at all. It exerts its pressure upwards 

 from below, whereas the others act downwards from 

 above ; and this is essential for a strong tight grip 

 (like that of a strong clamp), so that it may exert 

 a pressure equivalent to that of the other four. It 

 is short, then, first, for strength, but also because it 

 would be no good if it were long. (The end finger 

 also is small — this is as it should be — and the middle 

 one is long like an oar amidships, because any object 

 which is being grasped for active use has to be 

 grasped right around the middle.) And on this 

 account it is called " bi"; " althouo;h it is small, be- 

 cause the other fingers are practically useless without 

 it. The nails, too, are a good piece of planning. In 

 man they serve as coverings : a guard, in fact, for the 

 tip of the fingers. In animals they serve for practical 

 use as M-ell.^ 



The joints of the arms in man bend in the opposite 

 direction to those of quadrupeds : this is to facilitate 

 the bringing of food to the mouth, and other uses to 

 which they are put. Quadrupeds must be able to 

 bend their fore Hmbs inwards '^ so that they may be 

 serviceable in locomotion, since they use them as 



'' That is, as tools. 

 « See note on 693 b 3, p. 433. 



' 375 



