112 THE MECHANICAL FUNCTIONS OF THE FOOT. 



sideiable added load, and are hence exposed during severe work 

 to many chances of injury and disease. 



The action of weight on the hoof differs at a slow walk and 

 at higher rates of speed. At a walk the rise and fall of the 

 load is slight, but at the trot, gallop, or leap it greatly increases. 

 At these paces tlie impact of the body- weight is violently trans- 

 mitted to the lower parts of the limbs, and, in proportion to 

 the rapidity with which the animal moves, the hoof suffers a more 

 or less violent shock at each contact with the earth, such shock 

 producing in its turn a corresponding counter-shock. Considering 

 the weicfht of the animal's bodv, it is clear that, were it not for 

 the peculiar anti-concussive arrangements in the hoof and limb, 

 such violence must be followed by severe injury both to limb 

 and trunk. The angular formation of the limbs, and the 

 position in which they come in contact with the earth, the 

 presence of joints, and the excentric form of their articular 

 surfaces, the resiliency of articular cartilages, the lubrication by 

 synovia, the elasticity of ligaments, of the lateral cartilages, 

 plantar cushion, coronary band, and horny capsule, and, 

 finally, the peculiar union between hoof and pedal bone, all 

 co-operate in diminishing the effects of violent impact with the 

 earth, and in preventing transmission of shock to the trunk. 



An exhaustive examination of these anti-concussive media 

 would extend to even more distant regions, for the entire limb 

 is elastic, while the fore-limbs are connected with the trunk, 

 not by bones, but by muscles, a device which, in itself, tends 

 very materially to minimise shock. The hind-limbs, certainly, 

 are directly connected with the rest of the skeleton, but this is 

 compensated for by their angular formation, and by the ligament- 

 ous tissues connected with the stifle and hock joints. In every 

 joint, therefore, the vibration transmitted to the limb is some- 

 what diminished, and, as a consequence, the body sustains only 

 slight and unimportant disturbance. Of the lower joints of 

 the limb, the fetlock shows this anti-concussive mechanism 

 best. Its articular depression, into which fits the lower 

 extremity of the metacarpal bone, consists of three bones, con- 

 nected together, but nevertheless relatively movable. By 

 means of the powerful suspensory ligament, the sesamoid bones 

 are suspended from the bones of the carpus, and are connected 

 to the upper end of the metacarpus ; hence, when the fetlock 



