LECTURES ON HORSES. 
611 
correctness of the opinion of veterinary surgeons on this curious 
piece of mechanism. They imagine that these moveable splint 
bones, by playing up and down, as the foot is alternately raised 
and pressed to the ground, bestow elasticity, and prevent concus- 
sion. The fact certainly is, that by over-action this part becomes 
inflamed, and the extremities preternaturally joined by bone to the 
greater metacarpal or cannon bone ; and that this, which is called 
a splint, is a cause of lameness.” 
“ I suspect, rather,” continues Sir Charles, “ that, in a perfect 
state of the joint, these lesser metacarpal bones act as a spring to 
throw out the foot when it is raised, and the knee bent. If we 
admit that it is the quickness in the extension of this joint on 
which the rate of motion must principally depend, it will not escape 
observation, that, in the bent position of the knee, the extensor 
tendons have very little power, from their running so near to the 
centre of motion of the joint; and that, in fact, they require some 
additional means to aid the extension of the leg.” 
“ Supposing that the head of the lesser metacarpal bone,” says 
Sir Charles, in explanation of the above, “ enters into the compo- 
sition of the joint, it does not appear that, by its yielding when the 
foot is upon the ground, the bones of the carpus can descend, as 
long as they are sustained by the greater metacarpal or cannon 
bone ; I do not, therefore, conceive that this bone can add to the 
elasticity of the foot. But when we perceive that the head of the 
splint bone is behind the centre of motion in the joint, it is obvious 
that it must be more pressed upon in the bent position of the joint 
when the foot is elevated, and that then the bone must descend. 
If the splint bone be depressed when the limb is raised and bent, 
and have a power of recoiling (which it certainly has), it must 
aid in throwing the leg into the straight position, and assist the 
extensor muscles of the knee. Further, we can readily believe 
that, when the elasticity of these splint bones is lost, by ossification 
uniting them firmly to the cannon bone, the want of such a piece 
of mechanism essential to the quick extension of the foot will 
make the horse apt to come down.” 
Supposing the horse’s foot to be placed upon a perfectly level 
unyielding surface, and the weight from above to be thrown upon 
the limb in a direct line with the centre of motion, “ it does not 
appear,” as Sir Charles has observed, “ the bones of the carpus can 
descend.” But, supposing the animal’s foot to be placed upon an 
uneven surface, or upon one that becomes so by yielding, may there 
not be such tilting of the carpal bones from the one-sided dispo- 
sition of the weight expected to take place as will press downward 
the splint bone of one side, and so bring both bones into operation 
alternately or incidentally, as the case may be, depending upon the 
