68 



MECHANISM OF EQUINE LOCOMOTION. 



easy walking and gentle trotting, they may be observed to act energeti- 

 cally in flexing and extending the loins when the animal is leaping and 

 galloping, and when his powers are taxed in drawing a heavy load. 

 Any one who has ridden races or gallops on speedy thorough -breds, 

 will know from experience the immense power behind the saddle pos- 

 sessed by animals of this class ; for the rider cannot fail to feel the 

 vigorous " lift " given by the loins at each stride. 



I 



cu 



*' 



i 



Fig. 43. — Lateral Displacement 

 of Body. 



It is a popular fallacy to imagine that the muscles over the loins are 

 propellers. They have no propelling power at all ; for they are not 

 connected either with the thigh bone, or with any of the bones of the 

 limb below it ; their office in locomotion being merely to regulate the 

 weight on the fore-hand. The muscles under the loins (those which 

 constitute the under-cut in a saddle of mutton, or in a sirloin of 

 beef), draw the thigh forward. 



Width between each respective Pair of Legs as 

 affecting Speed. — Let us suppose that the rectangle a d e b (Fig. 

 43) diagrammatically represents the body of the horse ; that the fore 

 limbs are placed at fhe angles a and h ; that the hind limbs are at d 

 and e ; and that the centre of gravity is at c. Were both fore legs and 

 both hind legs to act respectively at the same moment, we would have 

 the centre of gravity moved in a straight line, and in the direction in 

 which the animal's body was placed. In the amble (p. 104), the pro- 

 pulsion is given through a and d, and through h and e alternatel}^ with 

 the result, in the former case, that the centre of gravity is displaced to 

 the right ; and in the latter, to the left. In the trot (p. loi), the alternate 

 strokes are through a and e, and b and d. If these respective propulsions, 

 in the trot, were equal to each other, and if the centre of gravity were 

 midwa}^ between the fore and hind legs, there would be no displacement 



