56 LEVERS. 



Acting on the principle just enunciated, the cart-horse, with the view of 

 obtaining all the mechanical advantage he can when trying to draw a heavy 

 load, will naturally endeavour to move the levers of his limbs (when 

 straightening them out) with the power, as nearly as possible, at right angles 

 to each respective lever. Hence he will obtain his results by only slight 

 bending of the joints, and consequently his steps will be short. We may see 

 tins action of the levers of the hind limbs well shown by the manner in which 

 he will crouch down behind when he makes a strong effort with his hind 

 legs while exerting the fore legs but little, as may occur when the roadway is 

 slippery. The galloper, on the contrary, will require the power of straightening 

 out his limbs to their utmost extent {see p. 63), and will thus obtain speed 

 at a lavish expenditure of muscular effort. This is especially well shown 

 in the action of the fetlock joint {see Fig. 29) ; for if the pastern be long 

 and sloping, the mechanical disadvantage will be great, but the gain in 

 speed will be equally large. If the pastern be upright, the fetlock will 

 work advantageously as far as the weight to be moved is concerned ; but 

 it will contribute little to the attainment of speed. 



