STRAIGHTENING OF THE LIMBS IN LOCOMOTION 51 



instance) have been slight horses. In fact, the son of Galopin and St Angela 

 (Figs. 9 and 229) had singularly light hind-quarters. Even Ormonde, who 

 was very nauscular for a race-horse, was anything but broad when viewed from 

 behind. 



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 the 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 unappreciable. 

 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 Marey's statement (p. 4), that muscles 

 of speed are long muscles. Besides this, 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. 



I need hardly say to those of my readers who have followed me so far, 

 that the greater the ability to straighten the leg, the higher will be the speed 

 of propulsion, and vice versL Hence, if a horse is, for instance, unable 

 from peculiarity of conformation to straighten his hocks (a condition called 

 "sickle-hocks," p. 210), he will not be so fast as he would have been, had 

 he greater freedom in these joints. We may test the truth of this principle in 

 our own selves ; for if, when swimming in a bath (p. 47), we wanted to touch 

 and turn, but were unable to straighten our knee on account of an injury 

 or from some other cause, we would be capable of giving only a comparatively 

 poor kick-off. The great beauty of a "straight-dropped hind leg" in the 

 horse, as a conformation favourable to speed, will again be alluded to on 



p. 210. 



The action of the fore limb in raising the fore hand, which is essential for 

 the regulation of the position of the centre of gravity in locomotion, is also 

 dependent on its difference of length when bent and when straightened out. 

 It is manifest that this difference is mainly due to the action of the shoulder 

 joint and of the fetlock. Hence, oblique shoulders and sloping pasterns are 

 " points " of speed and of leaping power. If the shoulder-blade and pastern 

 be upright, the limb will be capable of but slight extension. 



In heavy draught, full straightening out of the limbs is not desirable ; for 

 the last part of this action is accomplished at a great mechanical disadvan- 

 tage, to which I have alluded on page 45. At present it is sufficient to 

 compare the action of the limbs to that of the oars of a boat, in which the 



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