330 A Manual of Veterinary Physiology. 



When a man is on the horse's back, it is found that 66 

 per cent, of his weight is carried on the fore-legs, and 

 34 per cent, on the hind; the amount of weight on the 

 fore-legs is increased by leaning forward in the saddle, and 

 decreased by leaning back. 



An explanation why fore-legs are worn out earlier than 

 hind is afforded us by Avhat we now know of the physiology 

 of locomotion, viz., the fore-legs act as propellers of the 

 body, and owing to their being close to the centre of 

 gravity, they bear the largest share of the weight of the 

 body and the weight of the rider. 



In the act of standing the body is supported on four 

 props ; two of them have only a muscular attachment to the 

 trunk, the other pair are united by a ball and socket joint. 

 It is unnecessary to allude by name to the muscles con- 

 necting the fore-leg with the trunk, excepting to mention 

 the serratus magnus, through the medium of which the 

 body is principally slung on the scapula. 



No matter what the position of standing may be, or the 

 condition under which the horse is standing, he never in a 

 state of health keeps his fore-feet in any other position 

 than together ; one fore -limb advanced in front of the other 

 is abnormal. On the other hand, it is very rarely that one 

 ever sees a horse standing square on both hind-legs, he is 

 invariably resting the limbs alternately. Some years ago I 

 drew attention* to this as being an explanation of the 

 exemption of the hind-limbs from navicular disease. By 

 this process of resting, the compression of the navicular 

 bone between the body and the perforans is relieved. The 

 horse only learns to do it in the fore-legs when too late. 



When the horse is feeding off the ground, he always has 

 to advance one fore-leg a considerable distance in front of 

 the body, owing to the shortness of his neck. 



In the act of standing the rigidity of the bony column of 



the leg is maintained by the extensor tendons, each phalanx 



having an extensor attached to it, viz., the extensor meta- 



carpi leading to the large metacarpal bone, extensor pedis 



* Veterinary Journal, 1886. 



