LOCOMOTION OF MAMMALIA. 6!) 



afford a firm fulcrum to muscles passing from the caudal vertebrai 

 to the pelvis and hind-limbs : the short fore-limbs are tucked up 

 to the chest so as to offer the smallest surface to the air, and the 

 animal progresses in a series of bounds by simultaneous move- 

 ments of the hind-limbs. 



The Rabbit, in moving slowly, advances the fore-feet two or 

 three steps alternately. The body being thus elongated, the hind- 

 legs are suddenly extended and drawn forward simultaneously : it 

 thus, as it were, walks with the fore-legs, and leaps with the hind. 

 The Hare is under disadvantage with its long hind-limbs in 

 running down-hill, owing to the great inclination of the axis of 

 the trunk to the plane of motion, and it usually zigzags as it 

 descends ; but it gains proportionally in the ascent, and its speed 

 on level ground, through the size and strength of the chief pro- 

 pelling limbs, is very great. The degree of flexion of the trunk 

 accompanying the movements of these and other quadrupeds is 

 indicated by that in which the neural spines converge toward the 

 single vertical one marking the centre of motion, and it is 

 commonly greatest in the unguiculate quadrupeds. 



The vertically of the long and narrow tarsus and metatarsus 

 producing the ( digitigrade ' character of the type Carnivora, com- 

 bines with the geometrical and physical relations of the other parts 

 of the limbs to give them their superior speed and agility. In the 

 Dogs and Cats the oblique scapula, being unfettered by bony 

 (clavicular) connection with the sternum, enjoys the freedom of 

 rotation which characterises it in the swift Ungulates. The 

 humerus in the Lion (vol. ii. fig. 337) has its axis directed down- 

 ward and backward, forming with that of the scapula an angle of 

 110°. The olecranon projects so far behind the axis of rotation 

 in the elbow-joint as to constitute a powerful lever for the exten- 

 sors of the fore-arm. The hind-limbs are longest, and the bones 

 are inclined more obliquely to each other than in the fore-limbs, 

 subserviently to elasticity and power in springing. The calca- 

 neum is produced on the same principle as the olecranon, but 

 forms the more powerful lever of the two. The last perfection is 

 given to the limbs of Carnivora by the modifications of the toes of 

 Felines, whereby their tread is noiseless, and the claws exempt 

 from the wear and tear of progressive motion. It is effected by 

 a joint allowing the ungual phalanges to be brought in extension 

 above the middle phalanges, elastic ligaments being adjusted to 

 keep the joint so extended, and by a thick cushion of soft elastic 

 substance beneath the joint or parts of the phalanges transmitting 

 the superincumbent weight to the ground. 



