COMPARATIVE SPEED IN THE ACTION OF THE LIMBS. 65 



It is evident that the less the fall and rise at each step, the lower 

 this supposititious hill would be, and consequently, the easier it would 

 be to walk over. 



Although the duty of forward propulsion is chiefly performed by the 

 hind limbs ; the greater part of the work of adjusting the position of 

 the centre of gravity during ordinary locomotion, falls on the fore legs. 

 When a horse, for instance, performs the high-school feat of cantering 

 to the rear, the respective roles would obviously be reversed. The 

 question of the adjustment of the centre of gravity of the body, so that 

 the muscles of locomotion may act to the best possible advantage, will 

 be considered further on. 



Comparative Speed in the Action of the Limbs. — The speed 

 with which the body is projected forward, is directl}- proportionate to the 

 speed with which the limb or limbs are straightened out, and has nothing 

 to do with the strength of the muscles that move the parts. Hence, 

 any excess of muscular development beyond that required for the due 

 working of the limbs, will tend to diminish the speed by unnecessarily 

 adding to the weight to be carried. For this reason, we never see great 

 race-horses of the weight-carrj'ing hunter build. Some of the best 

 (St. Simon and Tim Whitfler, for instance) have been slight horses. In 

 fact, the son of Galopin and St. Angela (Figs. 16 and 17) had singularly 

 light hind-quarters. Even Ormonde, who was very muscular for a 

 race-horse, was anything but broad when viewed from behind (Fig. 3S4). 



The question of the speed of muscular contraction is an abstruse one 

 which still remains unsettled. We know that if a muscle be stimulated 

 by a shock of electricity, it will contract throughout its entire length 

 at (practically) the same moment. Hence, under this condition, a long 

 muscle would contract very nearly in the same time as a short one. 

 When, however, a muscle is stimulated by nerves which act in 

 obedience to the will, the contraction of its various parts does not take 

 place simultaneously, though at such a brief interval that we may 

 regard the delay as inappreciable. Hence, in two limbs which resemble 

 each other in every particular, except that one is short and the other 

 long, the respective extension of both will be accomplished in very 

 nearly the same time, and consequently the speed of the propulsion 

 derived from the long leg will exceed that from the short one, in nearly 

 the proportion which their lengths bear to each other. This conclusion 

 is in accordance with the statement that muscles of speed are long 

 muscles. Besides, physiology teaches us that the thicker muscles 

 are, the slower, other things being equal, do they contract on 

 becoming stimulated. We should content ourselves with taking a 

 broad view of this subject ; for conditions vary so much in individual 

 cases, that it is not safe to dogmatise on it. 



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