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LOCOMOTION OF ANIMAIA 



LOCOMOTION OF ANIMALS. 



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A little consideration will clear up the error into which Borelli 

 and others bare fallen respecting the horse. It will be observed 

 from the foregoing statement that the left hind leg moves first ; the 

 right fore leg second ; the right hind leg third ; and the left fore leg 

 fourth. Now if we do not analyse this order of motion from its 

 commencement, we may easily be deceived ; for in walking by a horse, 

 the two legs appear indeed to move together on the same side, but 

 thu arises from the continuity of the series of movements, which we 

 find begins with the left hind leg, and terminates with the left fore 

 leg; the movement of the right fore leg being in like manner 

 followed by that of the right hind leg ; which continuity of move- 

 ment, if not carefully discriminated, gives an impression that the 

 animal moves both legs on the same side simultaneously. 



The Trot, In trotting the horse moves its legs in pairs diagonally : 

 thus, if the legs a d (Jig. 36) be raised and advanced first, the legs 6 e 



will be raised the instant those desig- 

 ** S8> nated by a d reach the ground. On 



the other hand, when the legs 6 t are 

 raised before the legs a d reach the 

 ground, there is a minute interval 

 during which all the legs are raised 

 above the ground at the same time. 

 In trotting each leg moves rather 

 more frequently in the same period 

 of time than in walking, or nearly 

 as 6 to 5. But the velocity acquired 

 by moving the legs in pairs, instead 

 of consecutively, depends on the cir- 

 cumstance that, in trotting, each leg 

 rest* on the ground a short time, and swings during a long one ; whilst 

 in walking, each leg swings during a short period, and rests during a 

 comparatively long one. In walking, the trunk oscillates laterally, 

 whereas in trotting it oscillates vertically ; but in each of the* kinds 

 of movement there appears to be a slight motion of the trunk of the 

 animal both laterally and vertically. 



It may be observed that the vertical line traversing the base of 

 support passes through the horse in such a manner as to leave by far 

 the greater part of the weight of the body to be supported by the two 



The Gallop. In galloping, the horse adopts three different methods 

 of using iU organs of locomotion, which are distinguished by the 

 number and the order in which the feet reach the ground. 



First order of Motion. When a horse begins to gallop on the right, 

 the left hind leg reaches the ground first ; the right hind leg and left 

 fore leg next follow at the same time, and the right fore leg last This 

 is called the gallop of three beats. 



Second order of Motion. If the four legs roach the ground in sue- 

 cession, the left hind foot reaches the ground first, the right hind foot 

 second, the left fora foot third, and the right fore foot fourth. Thin 

 is the gallop of four beats, sometimes denominated the canter. This 

 order of movement is not adapted for great speed, but is an agreeable 

 motion in riding on horseback for ladies, or for gentlemen who ride 

 lazily or badly. 



Third order of Motion. In this kind of action the horse moves the 

 legs in the same order as in trotting ; that is, the left bind and right 

 fore feet reach the ground simultaneously, then the right hind and 

 left fora feet. This is the order in which the feet move in racing, and 

 whenever the greatest speed is required. It is called the gallop of two 



Leaping. In leaping, the horse raises the fore legs from the ground, 

 and projects the body upwards and forwards by the hind legs alone. 

 It is well known that they leap rivulets, hedges, and ditches with 

 great ease, even under the burden of heavy riders ; but to accomplish 



this an enormous expenditure of muscular action must be required ; 

 since the muscles which produce the effect act at a great mechanical 



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Horses which are constituted for great speed have the shoiil'U-r- 

 jointe directed at a considerable angle with the arm. Saintbell haa 

 given the relative proportions of the several parts of the skeleton of 

 the celebrated race-horse ' Eclipse,' together with the angles of inclina- 

 tion and range of motion belonging to the joints of the legs. Accord- 

 ing to his account, that hone, when galloping at liberty, and at iU 

 greatest speed, passed over twenty-five feet at each step : these stride* 

 were taken two and a half times in a second, being at the rate of about 

 four miles in six minutes and two seconds, or forty miles in an hour 

 and twenty seconds. 



Those quadrupeds are best adapted as beasts of burden, or to take 

 long and often repeated journeys, which have the anterior and posterior 

 limbs of nearly equal length, such for instance as the horse, ass, camel, 

 and many other aniinaU), and these have also the power of ascending 

 and descending hills with ease and safety. But such is not the cam; 

 with those quadrupeds in which the length of the anterior and posterior 

 extremities is remarkably disproportionate. The hare, for example, 

 has the hinder legs much longer than the anterior ones ; the conse- 

 quence of which is that, when pursued, it can often outstrip the 

 grayhound in running up the sides of hills ; but in descending it must 

 run iu a sflfczag direction, or it would tumble over. The rabbit pre- 

 sents the same conformation. In the jerboa and kangaroo the length 

 of the posterior legs predominates exceedingly over that of the anterior, 

 and their mode of progression is effected by a succession of leaps pro- 

 duced by the simultaneous action of their hinder extremities. \Vln-n 

 pursued the jerboa is said to clear uino feet at each leap, and mi 

 rapidly that the Cossacks, though mounted on the fleetest horses, are 

 unable to overtake it Iu these leaps the body flies through t \ 

 with the legs inclined backwards, as in .liy. .'IT, number 7. 



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In the kangaroo the length of the hind legs is nearly double that 

 of the foro legs, which is a disproportion far too great to permit them 

 to move with the same advantage as other quadrupeds. When the 

 kangaroo rests on its four legs the head and trunk incline to the 

 ground, as seen in number 8. They usually bit on the two hauiu h. -, 

 u.-ing the tail as the third leg of a tripod, as iu number 0. 



Amongst the Jiuminantia, the deer and the antelopes are beautifully 

 organised for speed ; but as they move on the same principles as the 

 horse, we need not stop to dwell on them. 



It may be remarked that those animals which are least furni -In .1 

 with the means of defence, and arc least protected, are often endowed 

 with the greatest speed of motion, Mich as the hare, antelope, deer, 

 ,\ ,-. On the other hand, the lion, tiger, leopard, and carnivorous 

 quadrupeds which are endowed with great strength, have not the 

 speed of the above-mentioned animals. This shows that, with the 

 same number of locomotive organs, the speed of an animal depends on 

 other conditions besides mere strength. The structure of the several 

 joints ; the relative length of the different portions of the limbn ; 

 the proportion which the length of the limbs bears to that of the 

 body ; the angular disposition of the limbs with respect to each other ; 

 the distances at which the muscles act with respect to the axes of thu 

 jjints; all concur to modify the speed of an animal, independently of 

 its muscular power. 



Birds. As birds are constituted for three kinds of locomotion, that 

 in, in air, in water, ami on dry land, it is obvious that they must have 

 organs adapted for these several kinds of progression. Their arms, 

 which form the wings, are not organised to be employed for prehen- 

 sion, as in man, or for moving on them in the manner of quadruped*. 

 Birds are essentially bipeds when moving on solid surfaces ; and OH 

 the feet of birds are so constituted that the toes only reach the ground 

 they may be denominated Digitigmde Bipeds. 



