SPEED 



193 



Through the columns of bones the propulsion is directed, and of these 

 in the horse two sets are in operation. The limb producing a forward and 

 upward movement being invariably directed backward and downward, must 

 necessarily act in the direction stated. 



The impetus obtained from the horse's fore-leg is through the humerus 

 and elbow-joint, while that of the hind-limb is through the medium of the 

 hip-joint and pelvis. 



SPEED 



a 



Speed is not due to the strength of 

 the muscles, or we should find strong 

 cart-horses with light bodies competing 

 with the blood-horse. It is due to the 

 rapidity with which the limbs can be 

 straightened out in contact with an 

 immovable body. 



With few exceptions, it may be said 

 that animals of great speed have long 

 limbs and slender muscles, while those 

 possessed of great strength have short 

 limbs and thick muscles. A comparison 

 between the race-horse and dray-horse, 

 or between the greyhound and bull-dog, 

 will serve to illustrate our meaning. 



Upon the distance through which 

 the centre of gravity is moved, in the 

 various paces, depends the degree of 

 fatigue produced. Where there is a 

 period of suspension all the legs being 

 clear of the ground (Plate XII) the 

 centre of gravity is necessarily raised, 



and thus it follows that the fast trot, canter, or gallop over a given dis- 

 tance takes more out of a horse than the walk or slow trot, where there 

 is no such period of suspension. 



The raising of the centre of gravity in each of the paces where there is 

 a period of suspension is exactly equal to its fall (or vice versa). 



The changing of the centre of gravity from one side to the other is 

 facilitated by the head and neck acting as a balance. The muscles con- 

 necting the head and neck with the trunk assist in raising the fore part 

 of the body during locomotion. 



Fig. 530. Action of the Flexor Muscles and 

 Tendons of the Fore-Limb 



a, Flexor pedis perforans. b, Flexor pedis 

 perforatus. 



