190 THE HAND. 



motion round its axis may be sufficiently large, the ligament 

 of the articulation is extended farther down than ordinary, on 

 the neck of this bone, before it is connected to it ; and it is 

 very thin at its upper and lower part, but makes a firm ring in 

 the middle. This bone is also joined to the ulna by a double 

 articulation : for above, a tubercle of the radius plays in a socket 

 of the ulna ; whilst below, the radius gives the socket, and the 

 ulna the tubercle. But then the motion performed at the two 

 ends is very different : for, at the upper end, the radius does little 

 more than turn round its axis ; while, at the lower end, it moves 

 nearly half round the cylindrical end of the ulna ; and, as the 

 hand is articulated and firmly connected here with the radius, 

 they must move together. When the palm is turned uppermost, 

 the radius is said to perform supination : when the back of the 

 hand is above, it is said to be prone. But then the quickness 

 and large extent of these two motions are assisted by the ulna, 

 which, as was before observed, can move wilh a kind of small 

 rotation on the sloping sides of the pulley. This rocking motion, 

 though very inconsiderable in the elbow joint itself, is conspicu- 

 ous at the lower end of such a long bone ; and the strong 

 ligament connecting this lower end to the carpus, makes the 

 hand more readily obey these motions. 



The Hand. 



The hand comprehends the whole structure, from the end of 

 the radius to the points of the fingers. Its back part is convex, 

 for greater firmness and strength ; and it is concave before, for 

 containing more surely and conveniently such bodies as we 

 take hold of. One half of the hand has an obscure motion in 

 comparison of what the other has ; it serves as a base to the 

 movable half, which can be extended back very little farther than 

 to a straight line with the forearm, but can be considerably bent 

 forwards. 



The hand consists of the carpus or wrist ; metacarpus, or 

 part adjoining the wrist ; and the fingers, a*mong which the 

 thumb is reckoned. 



