THE HORSE IN MOTION. 85 



a continuous impulse in the direction of motion, the limbs must move, 

 at whatever pace, in such manner as best to attain that end ; that the 

 more rapid the motion, the more uniform must be the support. 



If the time occupied by a racing horse in going a mile be one 

 minute and forty seconds, and the length of stride twenty-five feet, 

 as represented of some horses, it would follow that he must be off the 

 ground a full half-second at each bound, and according to the law of 

 falling bodies he would, if he moved horizontally, during that time fall 

 a distance of four feet. But in the gallop he is supposed to be moving 

 by a succession of bounds in which he rises as far as he falls. This 

 would give one fourth of a second as the time of descent equal to one 

 foot of vertical fall to twelve and a half feet movement in a horizon- 

 tal direction, and a consequent deflection of the centre of gravity to 



that extent. 



We can imagine the effect that would be produced upon a railway 

 car of any description if, when going at the same rate, it should pass 

 over an obstruction that would produce such a deflection of the line of 

 motion ; and if instead of the railway car we substitute the horse, what 

 but a broken neck could be expected ? There is no suspensory lig- 

 ament, or back tendon, or joint of the body that could be submitted to 

 such a shock in a state of tension, and not go through bankruptcy 



It is this deflection in the line of motion that constitutes the great 

 obstacle to be overcome in all methods of locomotion. It is that 

 which retards the progress of a ship in a rough sea; a certain amount 

 of momentum is lost in every undulation, and power is spent in lifting 

 the ship against the force of gravity that might in a smooth sea be 

 spent in accelerating velocity. But a ship is an inanimate object 

 acted upon by inanimate forces, and though speed is sacrificed, there 

 is no exhaustion from waste of strength, as is sustained by all living 

 beincrs in contending against the law of gravity, which requires a 

 greater expenditure of force to arrest a body in its fall than is requu-ed 

 to sustain it in a state of rest. 



The most perfect method of quadrupedal locomotion, therefore, is 

 that in which the greatest speed is attained with the least expenditure 

 of vital force. This is found in those quadrupeds in which the devia- 



