467 
THK HAND—ITS MECHANISM^ ScC. 
Of the Tiadius and Ulna. 
The same wonderful design is seen in the radius and ulna. 
There is, indeed, something highly interesting in the conforma¬ 
tion of the whole skeleton of an animal, and the adaptation of 
any one part to all the other parts. 
In the human subject there is great and easy motion of the 
hand, and we might imagine it to be in the hand itself; but, on 
the contrary, the movements are divided among all the bones of 
the extremity. 
The head of the humerus is rotatory on the scapula, as when 
making the guards in fencing ; but the easier and hner rolling of 
the wrist is accomplished by the motion of the radius and ulna. 
The ulna has a hooked process—the olecranon or projecting 
bone of the elbow—which catches round the lower end of the hu¬ 
merus or arm-bone, and forms with it a hinge joint. The radius, 
again, at the elbow has a small, neat, round head, which is bound 
to the ulna by ligaments, as a spindle is held in a bush. This 
bone turns on its axis, rolling upon the ulna both at the elbow 
and wrist joint, and as it turns carries the hand with it, because 
the hand is strictly attached to its lower head alone. This roll¬ 
ing is what is termed pronation and sapination.’' 
Now such a motion as this would be useless, and a source of 
weakness in an animal that had a solid hoof. Accordingly, in 
the horse these bones are united together, and consolidated in 
the position of pronation. 
We are compelled to pass over much interesting matter on this 
subject, and hasten on to the 
Last Division of the Bones of the Arm. 
In the human hand, the bones of the wrist (carpus) are eight 
in number; and they are so closely connected, that they form a 
sort of ball, which moves on the end of the radius. Beyond 
these and towards the fingers, forming the palm of the hand, are 
the metacarpal bones, which diverge at their further extremities, 
and give support to the bones of the fingers. The thumb has no 
metacarpal bone, and is directly articulated with the carpus or 
wrist. There are thus in the hand twenty-nine bones, from the 
mechanism of w'hich result strength, mobility, and elasticity.” 
We shall now compare these bones with those answering to the 
same in the horse, which are universally admitted to be of beau¬ 
tiful design, and calculated for strength and elasticity, and espe¬ 
cially provided against concussion. Hear our author :—“ The 
bones of the fore leg of the horse become firmer as we trace them 
downwards. The two bones corresponding with those of the 
fore arm are braced together and consolidated, and the motion 
at the elbow' joint is limited tf) flexion and extension. The car- 
