Types A^fD Market Classes of Li\'e Stock 417 



laterally, and so the heels expand. When the horse places his foot on 

 the ground there occurs: (1) Contraction of the hoof at the toe- wall 

 coronet; (2) sinking of the sole, especially at its branches; (3) expan- 

 sion of the heels; (4) sinking of the bulbs of the heels. These four 

 movements constitute what is known as the "hoof mechanism." The 

 health of the foot is dependent on the normal and free hoof mechanism, 

 and it should not be hindered by improper shoeing or other causes. 

 Hoof mechanism breaks concussion and assists circulation. Concus- 

 sion is shock and counter-shock. These shocks must be diffused, and 

 this is cared for laterally in the foot by its changes in form. 



Photographs of race horses in action show that at speed the horse 

 sets the heels to the ground before the other parts of the foot. This 

 utilizes the elastic structures of the heels to the utmost, produces a 

 maximum of hoof mechanism, and absorbs the violent shock to the 

 greatest degree possible. 



Absorption of concussion. — Every step at the walk or trot results 

 in concussion between the ground and the front foot of the horse. 

 Were it not for certain arrangements for the absorption of this shock 

 or jar, the horse would soon be made worthless. Hoof mechanism is, 

 as we have seen, one of the means of scattering the shock, acting in 

 much the same way as a pneumatic tire on a vehicle. Another safe- 

 guard is found in a sloping pastern, which acts in much the same 

 manner as the spring under a carriage. Then there is the angle be- 

 tween humerus and forearm, and also between scapula and humerus, 

 which also act as springs. A sloping shoulder is useful in the same way. 



If you have ever ridden in a farm wagon over a rough road, stand- 

 ing on your heels, you can appreciate the tremendous wear which comes 

 on the legs of a horse with poor feet, straight pasterns, and straight 

 shoulders. Then if you shifted your weight to your toes and bent 

 your knees slightly, you found that your teeth stopped chattering and 

 your hat remained on your head. In other words, your change in posi- 

 tion changed the column of bones supporting your weight from a 

 straight, vertical column to a broken one with angles which acted as 

 springs and absorbed the jar. It is just so with a horse having good 

 feet and nicely sloping shoulders and pasterns. 



Defective conformations of the legs and efifects on action. — A line 

 around the hoof on the ground gives the area of the base of support 

 of that leg. If the center of the base of support of the leg is not directly 

 under the center of the weight falling on that leg, the side of the foot 

 nearest the point directly under the center of weight will be compelled 

 to do more than its share of the work. Therefore the leg of the horse 

 should be so set that the center of the base of support comes directly 

 under the center of the weight it bears. The fore legs should be so 



