MECHANISM OF THE FETLOCK JOINT. 



depressing it. Certain muscles of the neck draw the fore limb forward and 

 upward ; other muscles of the neck straighten out the head and neck, and 

 a third group bend them. 



Mechanism of the Fetlock Joint.— As Lecoq explains, " the weight 

 of the body, transmitted by the cannon-bone upon the upper articulating 

 surface of the long pastern bone, is the resistance to be overcome. The 

 fulcrum is the ground at the toe of the foot, and the power acts upon the 

 sesamoid bones, which are at the back of the pastern ; the shortening of the 

 flexor muscles being the cause of the straightening of the angle formed by 

 their tendons." The diagram given in Fig. 29 will show how this lever (one of 

 the second order) acts. In it we see that the distance between the power 

 and weight remains constant; but that their respective distances from the 

 fulcrum vary according to the slope of the pastern and hoof, and according 

 to the length from the fetlock to the toe. Hence {see pp. 52 and 54), the shorter 



F^~ — w 



Fig. 29. — Mechanism of Fetlock Joixt. 



is this line, the greater will be the mechanical advantage at which the back 

 tendons will act ; and vice versa. On the other hand, we may see that the 

 more is the mechanical gain, the worse will the fetlock act as a spring, which 

 function is all-important in saving the limb (especially the fore one) from 

 the injurious effects of concussion. It is evident that the distance of the 

 weight (or power) from the fulcrum (F) is influenced by the length and slope 

 of the pastern ; it being greatest when the pastern is long and oblique, 

 and least when that part is short and upright. I may point out that 

 increased growth of hoof, either at the toe or heel, will affect die slope 

 in question, and that the thickness of horn at the toe will, of course, 

 influence the length from the fetlock to the toe. As a practical point I may 

 remark that the toe (except in the treatment of some forms of disease) should 



