120 PHYSIOLOGY OF FARM ANIMALS [CH. 



the radius and the proximal row of carpals in horses which are 

 so affected. 



The Fetlock Joint. Here we have a yielding articulation due 

 to the two sesamoid bones. These bones help to bear the animal's 

 weight in a state of rest, and provide an anti-concussion mechanism, 

 saving the limb from jar when it comes to the ground. 



Postures and Movements of the Horse. 



When a horse is at rest the centre of gravity is stable ; when 

 it is in motion the centre oscillates backwards and forwards. If 

 we draw a vertical line passing through a point six inches behind 

 the shoulder and a horizontal line passing a little below the 

 shoulder, the centre of gravity is approximately where these 

 lines intersect. Thus the centre is nearer to the elbow than to 

 the stifle. When pulling a load the centre is in front of the point 

 in question; when backing a load it is behind it. In jumping 

 the centre is behind this point when the hind legs leave the 

 ground; it moves forward as the fore legs come to the ground. 

 And similarly with the other motions. 



It follows from the normal position of the centre of gravity 

 that the fore legs bear a greater proportion of the total weight 

 of the body than the hind legs, and it has been calculated that 

 when carrying a rider, the fore legs bear two-thirds of the rider's 

 weight and the hind legs one-third. It has been shown also that 

 the amount of weight carried by the fore and hind legs re- 

 spectively varies with the position of the horse's head. If the 

 head is held well up, the fore legs carry less of its weight than 

 if the head is drooping. It is important therefore to keep a 

 stumbling horse in hand, and not to give him his head too much. 



Standing. As already described the fore legs are connected 

 with the body by the great serratus muscles. The hind legs 

 have no such muscular attachments, but simple ball and socket 

 joints. The horse is enabled to rest in a standing position, and 

 thus to sleep while standing by the help of the suspensory and 

 check ligaments. The suspensory ligament arises by two heads 

 from the carpus and ujjper part of the cannon bone ; it divides 

 into two, a branch being attached to each sesamoid bone and 

 continued downwards and forwards, finally joining the extensor 

 tendon. Its function is to support the fetlock. Further, in order 

 that the muscles attached to the humerus may be relieved of 



