LOCOMOTION OF ANIMALS. 



LOCOMOTION OP ANIMALS. 



the accomplishment of every stop U Tory great, even when walking on 

 a perfectly horiiootal path ; but it become* much greater when 

 sn<iiiillii|), inelined surfaces, luoh aa climbing the ridea of hill* and 

 mountaina. Under theaa circumstances the spaed i* diminUhed, and 

 the muscular power U expended in railing the body upward*. During 

 tht* petrol the number of respiration*, a* well a* the number of put- 

 ntion of the heart in a second, augment*, and a feeling of 

 languor and fatigue communicate* to the pedestrian the convic- 

 tion that he ha* done a* much work a* hi* system will sustain 

 without danger of over-fatigue and too great a prostration of 

 strength a condition from which it often takes a long time to 

 recruit. On the other band, a due exercise of muscular action 

 in walking i* necessary, aa we have already seen, to the healthy 

 aud rigorous play of the several organ* of the human body. 



We now come to consider Running. The object of calling 

 into action the locomotive organ* aa we employ them in running 

 U to acquire a greater velocity than can be attained in walking. 



take* place, and the time in which the leg is resting on the ground is 

 shorter than that in which it hang* suspended from the tnink. 



We will now illustrate these periods by a diagram. In fig. 22 let 

 the upper line represent the motion of the left, and the under line 

 that of the right leg, in the act of running, the curved portion* being 

 the period* of the leg swinging in the air, and the straight portions 



Fig. 22. 



On 



investigation it i* found that the same motions of the body recur after 

 each double step a* in walking. In running, the time of action is divided 

 into two periods, in one of which the body is supported on one leg, 

 and in the other it i* not supported on either, and this constitute* the 

 principal difference between running and walking ; for in the latter 

 the body U always supported either by one or both leg*. 



Let u* now consider the motions of the legs in running, as we have 

 before done in walking, and for that purpose let us trace their action 

 from the beginning to the end of a step. When the hinder leg, on 

 which the trunk was supported, having been extended to it* greatest 

 length, i* raised from the ground and begin* to swing forward, we 

 observe that the foremost leg ha* not yet reached the ground, so that 

 both leg* are found swinging at the same time during a portion of the 

 step. When the foremost leg reaches the ground, which it does in a 

 vertical position, the trunk i* supported on it, and the hinder leg 

 continue* to oscillate forwards, whilst the supporting leg, having 

 turned on the ball of the foot as on a pivot, becomes stretched to its 

 extreme length, and is in its turn raised from the earth before the 

 swinging leg baa reached it; and when the latter is placed on the 

 ground and is fully elongated, so a* to be on the point of rising again, 

 a double step ha* been accomplished, the single step evidently ending 

 at the moment when the other leg reached the corresponding position. 

 The effect of both legs swinging limultaueously, though for a very 

 abort period, is, that in running the duration of the step is less than 

 the time of the half-oscillation of the leg, whilst, in quickest walking 

 it just exactly equal* it, and in ilow walking it is greater than this 

 emi-oscillatiun. Tbeae effect* will perhaps be made more intelligible 

 by the annexed fig. 21, where a represents (low walking, the straight 



FI. 21. 



portion* of the line being the time* when both leg* are on the ground ; 

 1 represents quickest walking, wherein each leg succeed* the other in 

 swinging without interruption ; and e running, wherein one leg begins 

 to awing before the other has finished swinging. The forces which are 

 employed in running, like those of walking, consist of extension, 

 gravity, and resistance. 



We an not able to propel the centre of gravity horizontally in 

 running, though the undulation* are found by observation to be lea* 

 than in walking ; for it is clear, that a* soon as both legs are lifted 

 from the ground it must fall during some portion of the time it i* 

 unsupported, and so form a series of curve*. If the legs were Inflex- 

 ible tew centre of gravity would describe a serie* of carve* as in fiy. 18. 

 The movement* of the body in walking and running more nearly 

 nble each other according a* the time* wherein both leg* 



are on the ground in the former cue, and both legs are in the air in 

 the latter, are diminished ; and the limit to which each of these 

 motions continually approaches in, when the body i* never without 

 support, but that support i* never more than one leg. A* the resist- 

 ance of the air to the motion of the body i* greater in running than 

 in walking, the trunk is more inclined in the path of motion, to keep 

 it in a state of equilibrium. 



In order to find the amount of the vertical undulations of the body 

 In running, the Messrs. Weber viewed the runner through a telescope 

 adapted for the purpose. They estimated the undulations of the body 

 to be from three-fourth* of an inch to an inch and a quarter, and the 

 time of a step to be from one-fifth to one-fourth of a second ; of tlii 

 time the body swings freely in the air one-tenth, and fall* one-fifteenth 

 of a second. If we calculate the space through which the body fall* 

 in the same time by the law of falling bodies, it will be found that 

 the centre of gravity descend* about eight-tenths of an inch. 



It ha* been seen iafiy. 14, that in walking, the period during which 

 the trunk i* supported i* longer than that in which the leg whilst 

 swinging is supported by the trunk. Mow, in running, the reverse 



the periods of it* resting on the ground, which periods are defined 

 by the cross line*. The number* 1, 0, denote that one or neither of the 

 legs is on the ground. The line between the first spaces 1 and 0, at 

 the left end of the figure, indicates the beginning of a step corres- 

 ponding with the description already given, that is, the instant when the 

 left leg is raised from the ground, and before the right has reached it. 



We observe that the chords of the curved lines, which represent 

 the periods whilst the legs are swinging, are sensibly longer than the 

 traight lines ; and if we remember that the resting leg rises from the 

 earth before the other touches it, we at once see that it could not be 

 otherwise ; and it also follows, from the same reason, that the straight 

 lines showing the portion of the step when the leg is on the ground 

 must be equidistant from the extremities of the curve* respectively 

 opposite to them. 



In running, the square of the length of the extended leg U equal 

 to the sum of the squares of the horizontal space described by the 

 centre of gravity during the time the one leg rests on the ground, and 

 of the height of the centre of gravity from the plane of motion at the 

 end of that time. 



When the forward swinging leg reaches the ground at the end 

 of each step, it must be in a condition to receive the falling trunk, 

 and be prepared to project it from the ground, to swing again in the 

 air ; for this purpose the centre of gravity must be in the vertical line 

 passing through the head of the thigh-bone and foot ; for if the centre 

 fell behind this line, the runner would fall backward* ; and if before 

 it, he would fall forwards. Such being the law which is found to regu- 

 late the attitude of the body and leg in running, it U a matter of 

 considerable importance that artists should understand this principle, 

 together with all the other laws by which the locomotion of man and 

 niml. in governed. It was in consequence of his being ignorant of, or 

 not attending to, these laws that some of Flaxman's figures were drawn 

 so unlike the reality, which is the more to be regretted because his 

 drawings of the human figure are considered as studies by young 

 artists. We give an illustration of this in fig. 23, which represents a 



Fig. 23. 





'I 



man in the act of running, where the line a c ii, whk h pax-ics through 

 the centre of gravity, lies far behind the foot (4), the base of support, 

 and being therefore unsupported, the man would fall backward*. In 

 f .ct, no person can be in the position of Flaxman's figure whilst in 

 the act of running without falling to the ground. The same fault i 

 observable in fig. 24, another of Flaxman's designs, intended to repre- 

 sent a man just on the point of running : the line through the centre 

 of gravity falls behind the foremost foot, and consequently if the 

 hinder leg be raised, the man must inevitably tumble backward*. 



In running, the length of a step increase* much more rapidly than 

 the time of It decreases, and hence we chiefly gain by pausing over a 



