7^0 



SHOEINa. 



from a meclianioal point of view upon the action of this muscle, 

 we shall perceive that we have a lever of the second order at work 

 (Fig. 180). We have the weight (W) impressed downwards by 

 the cannon bone ; the power (P) acting upwards by the pull on 

 the tendon due to the contraction of the muscle ; while the fulcrum 

 (F) is the ground at the toe. The relations of power and weight 

 in a state of equilibrium, are: — 



W 



WF : PF. 



Hence the farther away the toe is from a perpendicular drawn 



]' W F 



Fig. 1 80, — Mechanism of the Horse's Foot. 



through the pastern joint (when the animal is standing at rest), 

 the greater will be the strain thrown on the back tendons, both 

 when standing still and during movement. From this we may 

 draw the following practical deductions: — 



(1) That the longer the hoof is allowed to grow (supposing 

 the heel and toe to increase equally in length), the severer will 

 be the strain on the back tendons ; for the effect of this increased 

 growth will be to still further remove the toe beyond the per- 

 pendicular which passes through the fetlock joint. 



(2) A similar effect will be produced if the heels be lowered 

 without reducing the toe, or if a shoe with a thick toe and thin 

 heels be used. 



