26 



THE FIRST GREAT DIVISION. 



motion of the knee, is thereby shortened in equal proportion. A fatigue, similar to 

 that produced by the action of ascending, is occasioned by walking with a very wide 

 step. As the legs arc thereby placed considerably apart, the body sinks lower at 

 the moment of their separation ; and as it is necessary to raise the body proportionally, 

 when turning alternately on each leg, the fatigue is consequently greater. 



Man is not compelled to swing his arms greatly to assist his walking, except when 

 confined to a very narrow path from which he cannot depart, and then he employs 

 every means to correct the unsteady motion of the body. Apes always require the 

 assistance of their arms in walking ; and such as have these extremities longest, like 

 the Orang Outang (Pithecus Satyriis), and the Long-armed Jlonkey or Gibbou 

 (Pithectis lar), use them with the greatest advantage. 



Among Quadrupeds, the action of walking is performed in the following manner :^ 

 The ' articulations of the hind-legs are first bent slightly, and extended in order to 

 carry the body forward ; in which movement the extensors of the knee and heel par- 

 ticularly contribute. The breast is thrown forward by this movement, the fore-legs 

 incline backwards, and the animal would certainly fall, did it not instantly throw its 

 fore-legs forward in order to support itself. The trunk is drawn upon the fore-legs, 

 ■which are now fixed in this position, and the action of the hind-legs is again repeated. 

 But it must be observed that, in the action of walking, these movements are not per- 

 formed at the same instant, by the legs of each pair; for, in that case, the animal 

 would necessarily be completely suspended for a moment over the ground. Its motion 

 would then no longer be a walk, but a succession of leaps, particularly denominated a 

 full-gallop. On the contrary, each step is executed by two legs only, one belong- 

 ing to the fore pair, and the other to the hind pair. ^NTien the motion is performed 

 by the legs on the same side, it is called an amhh — when by legs on opposite sides, 

 s. pace. 



. During the amble, the body being alternately supported by two legs of the same 

 side, is obliged to balance itself to the right and left, in order to avoid falling, and 

 the right fore-foot moves to sustain the body, urged onwards by the right hind-foot. 

 It is this balancing movement which renders the arable of the Horse and Ass so agree- 

 itble to invalids. 



In the paccy the body is supported alternately by two legs placed in a, diagonal 

 manner. The right fore-leg is advanced to sustain the body, thro^vn forward by the 

 extension of the left hind-foot ; and at the same instant tlie latter bends in order to 

 its being moved forward. While these are raised, the right hind-foot begins to extend 

 itself, and the moment they touch the ground, the left fore-foot moves forward to sup- 

 port the impulse of the right foot, which again moves forward. 



Quadi'upeds having the fore-feet longer than the hinder, as may be observed in tho 

 Giraffe, or Camelopard, possess the chief strength of their body in the fore-legs, and 

 accordingly the principal impulse is given by extending the fore-foot. The Sloths, 

 and all animals which like them have the fore-legs greatly disproportioned to the 

 others, drag themselves onwards with a laborious and tedious movement, by first 

 extending the anterior legs, and then bending them so as to draw the body onwards; 

 and with the Sloths, this difficult motion is further increased by the imperfect articu- 

 lations and general feebleness of the hinder-legs. 



The legs of the RIammiferous Quadrupeds move forwards and backwards in planes 

 nearly parallel to the spine, and not far from the middle plane of the body upon which 

 the weight operates. On the contrary, in the Oviparous Q-uadrupeds, the- thighs are 

 directed outwards, while the bendings of the limbs take place in planes perpendicular 

 to the spine. In the latter case, the weight of the body acts with a much longer 

 lever in opposing the extension of the knee. These animals, therefore, have the 

 knees always bent, and the belly drags upon the ground between the legs. For this 

 reason they have received the name of Reptiles. 



The short leaps of the Hares, Rats, and particularly of the Jerboas, are occasioned 

 by the great length of their hinder as compared to the fore-legs. Indeed, their fore- 

 legs are so short, that had they not the precaution to make this prancing movement, 

 these animals would be thrown down by each impulse of the hind-feet. It is only in 

 ascending a hill, that they can be said to walk at all. Their movement on level ground 

 is performed by a succession of short leaps ; and when they attempt to walk slowly 

 upon level ground, they are compelled to move themselves by the fore-feet, and merely 

 to drag the hinder pair after them, "We may observe the latter movement in the 

 Rabbit, and still more distinctly in the Frog. 



The Otters, Beavers, Water Tortoises or Turtles, and other quadrupeds designed 

 for swimming, have the hinder-legs placed very far apart to facilitate the motion. 

 They are, therefore, impelled laterally, the line of motion becomes crooked, and the^ 

 trunk is urged^onwards from side to side, 



, In Leaping, the body rises entirely from the earth, darts into the air, and remains 

 suspended for a momentary period, depending for its duration on the force of projec- 

 tion. This movement is performed by the sudden extension of all the inferior arti- 

 culations, after they have undergone an unusual degree of flexion. Their rapid ex- 

 tension gives a violent shock to the bones composing the articulations. The impulse 

 is then commuuicated to the centre of gravity of the animal's body, and it is pro- 

 jected With a determined velocity depending on its weight. A leaping body is, there- 

 fore, a projectile which graxlually loses the acquired velocity by which it ascended, its 

 motion being continually retarded, and finally destroyed by the force of gravity exer- 

 cised by the earth. We are therefore enabled to ascertain the curve described by a 

 leaping body in the air, with the time and place of its descent, when the projectile force 

 and the force of gravity are given, and allowance made for the resistance of the air. 



All the animals which leap best have the hinder-legs and thighs much longer and 

 thicker than the anterior — the projectile force, and consequently the extent of the leap, 

 being regulated by the proportional length of the muscles. The surprising leaps of 

 the Kangaroo, Jeiboa, and Frog, are plainly owing to this cause. 



Tlie smaller animals leap much farther than the larger, in proportion to their size. 

 This must follow obviously, if it be considered that when the projectile force impressed 

 , on two bodies is in proportion to their different magnitudes, their velocity will be 

 equal, and that the extent of the space through which they pass depends entirely upon 

 their respective velccities. The leaps of small and large animals are therefore neaidy 

 eijual. 



Man and Birds are the only animals capable of leaping vertically or hopping, lie- 

 cause they alone have the trunk placed directly over the legs, and the direction of a 

 leap depends upon the situation of the centre of gravity, in respect to the member by 

 which the impulse is given. They are also capable of leaping forward, by impressing 

 a greater degree of force on the rotatory motion of the thigh than on that of the leg ; 

 or they may even leap backwards, by making an opposite exertion. On the contrary. 

 Quadrupeds can only leap forwards. 



Running differs from walking, only in the body being projected forward at each 

 step, and in the hinder-foot being raised before the anterior foot touches the ground. 

 It consists, in fact, of a series of low leaps performed by each leg. As the acquired 

 Telocity is preserved, and augmented at each bound by the new velocity thereby added 

 to it, running is more rapid than the quickest walking step. An animal cannot, there- 

 fore, stop itself instantaneously when running, though a stop may be made at each 

 step in walking. In leaping forward, a previous run is advantageous, because it adds" 

 the momentum acquired during the run to that obtained from the leap itself; but a 

 vertical leap or hop would be entirely prevented by a run, or at least consider- 

 ably diminished. For this reason, a horse in full gallop, preparing to leap,' 

 retards his velocity before making the spring. In running, an animal inclines 

 its body forwards, that the centre of gravity may be in a proper situation for re- 

 cei\'ing an impulse in that direction from the hinder-leg. It is also requisite 

 to move the fore-leg rapidly forward to guard against falling. Were any obstacle to 

 intervene, so as to prevent this leg from reaching the ground in time to support the 

 body, a fall would be the consequence. It also follows, that inten-uptions of this 

 kind are more dangerous in running than in walking, on account of the greater momen- 

 tum of the body, and for the same reason they occur more frequently. Man never 

 varies his manner of running, except in taking longer or shorter steps, or in giving 

 to his body a greater or less degree of velocity; but Quadrupeds vary their mode 

 of running, by the diiTerent order in which they raise each foot, or bring it to the 

 ground. 



The feet diagonally opposite rise simultaneously in the trot^ and fall at once, each 

 pair alternately, but in such a manner, that for a moment all the four feet are off the 

 ground. The sound of the animal's steps are therefore heard two and two in succes- 

 sion, and a regular motion is produced. 



The Dog, Hare, and many other quadrupeds, can only run in the manner particu- 

 larly denominated the full gallop, which is the most rapid motion of the Hbrse. These 

 animals raise the anterior feet at each step; the body is projected forwards by the 

 extension of the hind-feet; the two fore-feet descend at the same time, and are 

 followed by the two hind-feet also descending together. By this means, the steps 

 of the horse are heard by two beats at a time, differing in this respect from the 

 comvion gallop, where the two fore-feet are hfted unequally, and fall one after another, 

 and from those other varieties of the gallop, where the horse's footsteps are heard by 

 a series of three or four be;ds, from the hinder-feet falHng to the ground either both 

 together or one after the other, 



IVIany animals leap by organs different from feet, but they all agree in this respect, 

 that the movement is occasioned by the sudden extension of several articulations. 

 Serpents leap by folding their bodies into several undulations, which are unbent at 

 the same instant, according to the degree of velocity which they wish to impart to 

 their bodies. Only a few genera are assisted in this motion by the scales of the beily^ 

 which they are able to elevate and depress at pleasure. Some Fishes leap to the tops 

 of cataracts by bending their bodies strongly, and then unbending, them suddenly, so 

 that they rise with an elastic and powerful spring. 



Several animals, which in reahty leap, have been improperly said to fly. The 

 Flying Lemurs, Flying Squurels, and Flying Phalangers, have membranes between 

 the feet, but their toes are not elongated. These membranes serve to support them 

 for some time in the air, and enable them to take groat leaps in descending ; but the 

 membrane acts merely as a parachute, as these animals cannot raise themselves in the 

 air. In the same manner, the Flying Dragon, a small hzard found in the East Indies^ 

 supports itself for some moments during a leap, by a membrane sustained by a few 

 bony rays, articulated to the spine of the back. 



Slan and various other animals possess the power of seizing objects, by surround- 

 ing and grasping them T\-ith their fingers. For this reason, it is necessary that thft 

 fingers should be separate, free, flexible, and of a certain length. Man has such 

 fingers on his hand only; but Apes and some other kinds of animals have them both 

 on the hands and feet; hence they are termed quadriimana^ or four-handed. 



Man surpasses all other animals in the dehcate operations which his hand is capable- 

 of performing. The Apes and Lemurs alone possess with him a thumb opposable to tha 

 other fingers, and forming with them a kind of forceps. They are consequently tha. 

 only animals capable of holding moveable objects in a single hand. But it is indis- 

 pensable to perfect prehension that they should have the power of rotating the hand 

 upon the fore-arm, and the bones of the shoulder must be placed so as to prevent the 

 scapula or shoulder-blade from being thrown forwai'ds. 



The Squirrel, Opossum, Rat, and other animals, possess fingers suflSciently small 

 and flexible to enable them to take up objects, but they can only hold them by the 

 assistance of both paws. Dogs and Cats, which have the toes shorter, and besides 

 are under the necessity of resting on their fore-feet, can retain their hold of sub- 

 stances solely by fixing them upon the ground with their paws. Those animals havin" 

 the toes united and drawn together under the skin, or enveloped in horny hoofs, are 

 incapable of exercising any prehensile power. 



Climbing is greatly facilitated by a power of seizing and grasping firmly. Man is- 

 but an indiflterent climber, because he can only grasp with his hands. His feet ^re 

 chiefly adapted for supporting the body, and afford but an imperfect means of elevating 

 it by the extension of the knees and heels. The arms form, therefore, the chief 

 means of drawing the body upwards in climbing. 



Monkeys, and other Quadrumana, are the best climbers. They can seize equally 

 well with their four extremities; and the position of their hind-feet is still mora 

 favorable to this action, as the soles are turned inwards, instead of being directed, 

 outwards. Ant-eaters and Sloths have a considerable protuberance on the heeT,. 

 which nearly accompUshes the same end ; and with the Opossums and Phalangera. 



