42 SEATS AND SADDLES. 



the relative position of the various bones composing 

 them, furnish us with very clear proof of this same 

 vertebra being the real centre of motion when the 

 horse is in action. For there is one bone in each of 

 the hind and fore legs through which the remainder of 

 the limb acts as a lever on the whole frame, either for 

 the purpose of propelling it (hind legs), or supporting 

 and lifting it (fore legs). There are the thigh-bone t, 

 and the arm-bone v (fig. 4), whose upper ends have 

 their fulcrums or points of support in the hip-bones 4 

 and shoulder-blades D (Plate I.) respectively, the power 

 being applied through the medium of the remaining 

 portions of the legs at their lower ends. Now the 

 greatest result of lever action is exercised at a right 

 angle to the lever, and drawing the lines P Q and R S 

 through the lower ends of these two bones at right 

 angles to them, we find that they intersect (or cross) 

 each other precisely at this same fourteenth vertebra. 

 The figure shows us, indeed, the horse in a state of 

 rest, and not in action ; but it is necessary to remember 

 that the propelling action of the hind leg commences, and 

 is precisely more powerful, when the thigh-bone is in this 

 position, diminishing in intensity as the leg is stretched 

 out towards R, and the angles become flatter ; whereas, 

 on the contrary, the supporting and lifting action of the 

 fore leg ends, the arm-bone being as shown in the 

 figure, and is also most intense, diminishing as the fore 

 leg is stretched out towards P, and the angles become 

 flatter. It is therefore evident that, both in a state of 

 rest and of action , the fourteenth vertebra is constantly 

 the centre of motion ; and it is precisely from our prac- 

 tical knowledge of this beautiful mechanism that judges 

 of horses attach so much importance to the length of 



