26 THE HORSE IN MOTION. 



which surround the joints as a continuous collar, whose borders are 

 attached to each of the bones so far from the opposing surfaces as not 

 to intervene, and yet not so far that they may not limit the motion to 

 its needs. These capsular ligaments serve another useful purpose. 

 Being air-tight, when the limb is off the ground it is supported in its 

 place by the pressure of the atmosphere, estimated by Borelli to be 

 equal, in the hip joint of a man, to a lifting force of twenty-six pounds. 

 The force thus gained is set free to be employed in locomotion. Each 

 joint constitutes by itself an interesting subject for study, as they all 

 differ in some important particular, according to their uses. The 

 construction of the hock joint is quite unique, and has no analogue 

 in man ; and that of the hock of the ox is quite different from that of 

 the horse. The interlocking grooves are oblique, so that when the 

 posterior extremity is brought forward to pass its fellow, fixed upon 

 the ground, it is carried obliquely outward, independently of volition ; 

 and when all danger of interference is passed, and the limb is again 

 extended to reach the ground, the foot is carried obliquely inwards, to 

 resume its place under the centre of gravity. This will be referred to 

 more fully when considering the action of the posterior extremity. 

 The construction of the joints at large would serve as a subject for a 

 monograph of great interest; but to be fully understood it must be 

 studied ensis in manu. 



A detailed description of the bones will not be attempted. They 

 are proverbially a dry subject ; but for the convenience of those 

 who require it, a reference plate is presented, lithographed from a 

 photograph; and it is hoped that it will, through the eye, give the 

 necessary information to enable the reader to understand the mechan- 

 ical movements without the study which abstract description would 

 require. But the vertebra, or spinal column, as the keel or bed-plate 

 connecting the various parts of the machinery, requires further 

 attention. 



The term "spinal column," as applied to the skeleton of quadrupeds, 

 is a misnomer, derived, like most anatomical names in comparative 

 anatomy, from its analogue in man. The spine being horizontal 

 in quadrupeds, and not vertical, as in man, the term " column " 



