454 



MOTION. 



difference arises chiefly from the great length of 

 the tibia, which is nearly equal to that in the 

 Giraffe, the former being to the latter as 16'5 

 to 18 inches. In the Rodentia, as the Hare, 

 Agouti, and Guinea-pig, we observe a similar 

 disproportion in the length of the extremities. 

 The Rabbit, in moving slowly, advances the 

 anterior feet two or three steps alternately, the 

 posterior limbs remaining inactive. The body 

 having been elongated by this means, the 

 posterior legs are suddenly extended and drawn 

 forwards simultaneously ; thus, the rabbit walks 

 with the fore, and leaps with the hinder pair 

 of legs. Those quadrupeds in which the 

 length of the posterior extremities much pre- 

 dominates over that of the anterior, are ob- 

 served to descend declivities in a straight line 

 with difficulty, on account of the great inclina- 

 tion of the axis of the trunk to the plane of 

 motion, which puts the animal in constant 

 danger of oversetting; they therefore take a 

 zigzag course. In ascending a hill, however, 

 their progression is greatly facilitated by the 

 length of their posterior extremities. The speed 

 of the Hare is well known to be greater than 

 that of the fleetest horse or hound. 



Ruminantia. Many of the Ruminantia, 

 such as the Deer and Antelope, are beautifully 

 and symmetrically organized for rapidity of loco- 

 motion ; the Camel for prolonged power of tra- 

 versing the arid desert ; and the Ox for the 

 strength and development of its muscularsystem. 



Amongst the Ruminantia some species have 

 the neck of great length, and the head being 

 surmounted with massive horns, or antlers, 

 renders it necessary that the spinous processes 

 of the lower cervical and superior dorsal verte- 

 brae be lengthened, so as to form powerful 

 levers for the attachment of muscles, and of 

 that yellow elastic tissue, the ligamentum 

 nucha, which is greatly developed in the Rumi- 

 nantia, to support the head and its appendages ; 

 the latter acting at the end of a long lever tends 

 to throw the centre of gravity forwards nearly 

 between the anterior extremities. The figure 

 of the trunk is elliptical; its transverse axis dimi- 

 nishes as it approaches the anterior extremities; 

 there are no clavicles ; and from the small degree 

 of curvature of the ribs, the arms are thrown 

 almost together beneath the trunk, and nearly 

 in the plane of the mesial section of the body. 

 The Giraffe presents greater length of osseous 

 columns for the support of its superstructure 

 than is to be found in any other animal ; the 

 bones of the anterior extremity are directed 

 more vertically than those of the posterior, 

 which enable it to support, with less weight of 

 bone and less expenditure of muscular force, 

 its lengthened neck, upon which the head acts 

 as at the end of a long lever. The metatarsal 

 and metacarpal bones are of great length, and 

 being directed vertically, as in the Pachy- 

 dermata, the trunk is elevated to a great height. 

 The three phalanges of each finger and toe are 

 inclined forwards ; the extensor tendons act on 

 them by means of a pulley, through the inter- 



position of the sesamoid bones, which increase 

 the distance of the direction of the tendons 

 from the axes of the joints, and give them 

 greater power. 



The length of the arms to that of the legs 

 in the Giraffe is as 71 to 67 inches, which 

 gives a difference of four inches in favour of 

 the length of the arms. This disproportion is 

 further augmented by the lengthened scapulae, 

 and by the increased angular disposition of 

 the posterior extremities. 



In the Camel, the length of the legs is more 

 nearly equal than in the Giraffe, the anterior 

 being to the posterior limbs as 49 to 47 inches ; 

 the spine is consequently directed more hori- 

 zontally than in the Giraffe. The order in which 

 the movements of the legs succeed each other in 

 the Camel is like that of other quadrupeds. 

 The velocity of the camel at its common tra- 

 velling pace is estimated at 2^ miles an hour.* 



In Deer and Antelopes, the geometrical pro- 

 portions are such as to confer on them great 

 speed. The lightness, elegance, and strength 

 of their osseous fabric, the energy of their mus- 

 cular system, the freedom of motion in the 

 vertebral column, the large arc described in the 

 greatest rotation of the scapula and pelvis, the 

 length and proportions of their extremities, the 

 length of the olecranon and calcaneum, the 

 vertical direction and length of the metatarsal 

 and metacarpal bones, the inclined direction 

 and freedom of motion of the three phalanges 

 of the fingers and toes, the number and relative 

 distances of the joints, all conspire to perfect 

 the progression of these Ruminantia. They 

 bound by the sudden flexion and extension of 

 all the legs, which are lifted from the ground 

 simultaneously, and which, after projecting the 

 centre of gravity in a vertical direction, appear 

 to arrive again synchronously on the plane of 

 motion. They walk or trot upon the principle 

 of other quadrupeds, as explained already in 

 the Horse. The Deer and Antelope, celebrated 

 for speed, bound over plains, ascend or descend 

 mountains, and also possess the power of leap- 

 ing across an abyss of great breadth, or down 

 precipices twenty or thirty feet in depth with- 

 out sustaining the slightest injury from the shock. 



Proboscidiu. The enormous bulk of the 

 head and body, and massive proportions of the 

 osseous and muscular systems, are more largely 

 developed in the ponderous Proboscidia than in 

 any other known species of terrestrial quadru- 

 peds. The dimensions of the bones of the 

 extremities are proportional to the gravity of 

 the superincumbent weight; the scapula and 

 pelvis, as well as the axes of the scapulo-humeral 

 and ilio-femoral cavities, are directed nearly per- 

 pendicular to the plane of progression, and the 

 whole column in each extremity presents a less 

 angular disposition of the axes of the bones 

 than is found in the lighter and more agile 

 solidungulous Pachydermata. The olecranon 

 and calcaneum, as well as the trochanters, 

 afford long and powerful levers for the applica- 

 tion of muscular action. The ginglymoid 



same species of animals may ho considered nearly 

 constant for all age*, s\es, and magnitudes. 



* See Rennrl on the rate of travelling of camels. 

 Phil. Trans. 1791, p. 129. 



