E09 



LOCOMOTION OF ANIMALS. 



LOCOMOTION OF ANIMALS. 



Fig. 24. 



greater space in a given time. Messrs. Weber found that when the 

 time of the step was 0"'301, the length was about 1 foot, and when 

 the time was diminished to 0"'268, the length of step was about 

 5 feet, so that with a decrease of only thirty-three thousandths of a 

 second the velocity increased by more than a five-fold proportion. In 

 fact the time of a step in running differs scarcely in a perceptible 

 manner from that of quickest walking, it being nearly equal in both 

 canes to the duration of a semi-oscillation of the leg. 



Running requires a vastly greater expenditure of muscular force 

 than walking, and cannot be long maintained without completely 

 exhausting the strength. 



It appears that a man named Jackson some years ago ran a mile in 

 4 minutes and 54 seconds, so that he passed over rather more than 

 18 feet in a second, or at the rate of 12'3 miles in an hour, a velocity 

 very rarely exceeded. 



Leaping, Springing, or Jumping. In leaping, the object to be attained 

 is different from that of running. In the latter we aim at taking the 

 longest step in the least possible time, but in the former we want to 

 take the longest possible steps without regard to their duration, and 

 the longer the step the greater will be the time in taking it. In leap- 

 ing with both legs at thejsame time, as in jigs. 25 and 26, there must 



Figs. 25 and 26. 



be a pause between each step, and this is not resorted to as a mode of 

 progression, but rather to accomplish a single step of great length ; 

 for the expenditure of muscular action is so enormous, that a succes- 

 sion of steps with both legs, alternately resting on the ground and 

 lift<'<! from it together, is rarely had recourse to, except for such 

 purposes an leaping across rivulets or narrow chasms, descending abrupt 

 surfaces, &c. 



When the object in view is to maintain a mean uniform progressive 

 motion by leaping, the legs interchange their offices alternately as in 

 running. The step in leaping, like that in running, may be divided 

 into two periods, during the first of which one leg rests on the ground, 

 supports the body, and propels it upwards and forwards ; and during 



the second period, both legs swing in the air simultaneously. The 

 undulations of the centre of gravity are greater in leaping than in 

 walking or running, in consequence of the body being projected higher 

 into the air, whereby the swinging leg is enabled to pass beyond the 

 vertical line through the centre of gravity, and to perform the whole 

 of its arc of oscillation before it is placed on the ground ; whereas iu 

 running it is arrested at the instant when it arrives at the vertical 

 position; and this constitutes the principal difference between the 

 two motions. 



If we begin the step, as in running, at the moment when the hinder 

 leg, being fully stretched, projects the trunk upwards and forwards, 

 and itself quits the ground, we find the other leg still swinging, which 

 it continues to do for a much longer time than in running ; after the 

 latter has reached the earth, it rotates round the ball of the foot, and 

 from being iu an oblique position in front of the body, it comes into 

 a similar one behind it, the two extreme oblique positions forming 

 equal angles with the vertical. The first-mentioned leg has been all 

 this time swinging, and so continues after the other has left the ground, 

 and at length it comes to the earth obliquely, and rotates into the 

 position with which we commenced our description. 



As the swinging leg is suffered to perform an entire oscillation, it 

 follows that the duration of the step is greater in leaping than in 

 running, but in consequence of the greater length of the step, the 

 velocity in the former is not so much less than in the latter as might 

 have been expected. For example, let us suppose the length of the 

 step in running, as is found by experiment, to be 5 feet, and the time 

 of the step to be 0"'268, also the length of the step in leaping to be 

 6'485 feet, the corresponding time of which is 0"'404, then the velocity 



in running will be to the velocity of leaping as . to - , or as 



0-268 0-484 



1 to 0'718. Thus we observe the velocity of leaping to be less than 

 that of running, both being estimated at the greatest speed ; but then 

 in leaping, the steps, being taken in greater time, do not excite the 

 pulsations of the heart, or increase the number of respiratory move- 

 ments so much as in running ; and persons when fatigued with running 

 find that if they wish to relieve the respiratory and arterial systems 

 without materially slackening their speed, they can accomplish this 

 object by converting the running into a leaping movement, better than 

 by converting the quick into a slow running. 



It is found much safer to descend the sides of steep hills with rapi- 

 dity by means of small leaps than by running, because in the former 

 the foot may be placed on and pressed against the ground in advance 

 of the trunk, and so arrest its motion and prevent the body from 

 falling to the ground, which cannot be done in running. 



The movement in leaping, being of all the foregoing motions most 

 under control, is varied by the peculiar manner in which the step is 

 made, and is therefore not so susceptible of accurate demonstration 

 as those of walking and running. 



The laws which regulate the locomotion of man admit of mathe- 

 matical analysis, and those of walking and running are found to be 

 as fixed as those which govern the solar sytsem. 



Having given an outline of the mechanism by which the human 

 race perform their movements from place to place by means of then- 

 locomotive organs, and having also detailed the leading principles by 

 which these movements are effected, we shall now turn our attention 

 to the means and methods by which the locomotion of animals inferior 

 to man in the scale of organisation is performed. It will be convenient 

 to take in succession the lower animals in classes as grouped by zoolo- 

 gists, and begin with those which are most nearly allied to man. It 

 is true that by this arrangement we shall have to pass from bipeda to 

 quaarupeds, and trace our steps back again to bipeds ; but these objec- 

 tions will not embarrass our subject, as would the grouping together 

 of animals of widely different classes whose organs of motion are very 

 dissimilar, although they perform movements which involve some of 

 the laws common to each. In following the plan already indicated, 

 we arrive at a group of animals which excite no common degree of 

 interest iu the minds of zoologists, namely, the Quadrumana,. If we 

 take a glance at the solid bony framework, as represented in figs. 27, 

 28, 29, we shall at once see, without being acquainted with anatomy, 

 that the general outline is nearly the same in all the figures, and that 

 there are many parts in common, or having bones of similar figures, 

 in each of the three skeletons. Upon closer inspection however we 

 shall perceive that some bones are common to the three : some have 

 additional bones, such has an extra pair of ribs ; other bonea, again, 

 are common between fiys. 27 and 28, 27 and 29, and 28 and 29. On com- 

 paring heads in figs. 30, 31, and 32, we observe that the face and jaws 

 are much more extended anteriorly iu the chimpanzee (Jig. 31) than 

 in man ( jig. 30), and that they are still further prolonged in the orang- 

 outan (fy. 32) : the proportion in each may be obtained by taking in 

 each case the length of the lines x y. We see also that the forehead 

 is lower and the head flatter in the orang, and still more so in the 

 chimpanzee. The head of each turns by a hinge-joint on a pivot at 

 y; and in the erect position the distance of x y is least in man, 

 greater in the chimpanzee, and greatest in the oraug : and. as the force 

 necessary to support the head in standing erect is proportional to the 

 weight of the parts multiplied by their distance from the axis of 

 motion iu the direction of these lines, it follows that the power 



