IV. 10. 119 



Such capacity of divergence does not prevent their again con- 

 verging so as to form a single compact body, whereas had the 

 hand been an undivided mass, divergence would have been 

 impossible. Again these parts may be used singly or together, 

 and in various combinations. The joints, moreover, of the fingers 

 are well constructed for prehension and for pressure. One of the 

 digits also, and this not long like the rest but short and thick, is 

 placed laterally. For were it not so placed all prehension would 

 be as impossible, as were there no hand at all. For the pressure 

 of this lateral digit is applied from below upwards, while the rest 

 act from above downwards ; an arrangement which is essential, 

 if the grasp is to be firm and hold like a tight clamp. As for 

 the shortness of this lateral digit, the object is to increase its 

 strength, so that it may be able, though but one, to counter- 

 balance its more numerous opponents. Indeed were it long it 

 would be of no use. This is the explanation of its being some- 

 times called the great digit, in spite of its small size ; for without 

 it all the rest would be practically useless. The finger which 

 stands at the other end of the row is small, while the central 

 one. of all is long, like the centre oar in a ship. This is rightly 

 so; for in grasping an object,- as a workman grasps his tool, it 

 is the central part of the encircling hold which is of the most 

 importance. . 



No less skilfully contrived are the nails. For, while in man 

 these serve simply as coverings to protect the ends of the fingers, 

 in other animals they are also i}sed for active purposes ; [and 

 their form in each case is suited to their office.] ^^ 



The arms in man and the fore limbs in quadrupeds bend in 

 precisely ^^ contrary directions, this difference having reference to 

 the ingestion of food ^^ and to the other offices which belong to 

 these parts. For -quadrupeds use their anterior limbs as feet in 

 progression, and must therefore have them bent inwards. In such 

 of the quadrupeds indeed as are polydactylous, these fore limbs 

 are at any rate intended not only to serve in locomotion, but also 

 to act as hands. And they are in fact so used, as any one may 

 see. For these animals seize hold of objects, and also repel 

 assailants, with their anterior limbs ; whereas quadrupeds with 

 solid hoofs use their hind legs for this latter purpose.*^ For their 

 fore limbs are not analogous to the arms and hands of man.^" 



It is this hand-like office of the anterior limbs which explains 

 688a. 



