TYPES AND MARKET CLASSES OF LIVE STOCK 



353 



of six bones which may be divided into two sets, each having a 

 purpose of its own. One group of four small bones (tarsals), 

 arranged in two rows and resting on the head of the cannon, 

 are united together and to adjacent bones by short, powerfu 

 ligaments, and so close is the union that the movement of one 

 bone upon another is reduced to a simple gliding action of very 

 limited degree. Though slight, this movement is of much im- 

 portance in breaking the jar communicated to this joint when 

 the horse is in action. Above the small tarsal bones are two 

 larger bones, the astragalus and calcaneus, as shown in Fig. 112. 



Fig. 111. Bones, Tendons, and Ligaments 

 of the Fore Leg. 



1, Splint bone; 2, cannon bone; 3, sus- 

 pensory ligament; 4, flexor tendon of foot; 

 5, flexor tendon of pastern. 



Foot 



To the calcaneus is attached the strong tendon known as 

 the tendon of Achilles. By means of it the muscles above 

 exert a powerful pull upon the hock joint, producing extension 

 of the joint. This is the principal means of the horse's pro- 

 pulsion. The knob-like end of the calcaneus (to which the 

 tendon attaches) forms the point of the hock. In some in- 

 stances the pull upon the hock has been great enough to pro- 

 duce a fracture of this bone. 



Sometimes a diseased condition is brought about by the 

 ossification into one mass of some or all of the bones of the hock. 

 This is called a bone spavin and is a serious unsoundness because 

 it destroys the important gliding action of the tarsals, stiffens 

 the joint, and often causes lameness. 



