MODES OF PROGRESSION. 91 



animals, as the giraffe, the lama, and the bear, raise both 

 legs of one side at the same moment. This is called am- 

 bling, or pacing. 



188. RUNNING consists in the same succession of motions 

 as walking, so accelerated that there is a moment be- 

 tween two steps when none of the limbs touch the ground. 

 In the horse and dog, and in most mammals, a distinction is 

 made between the walk, the trot, the canter, and the gallop, 

 all of which have different positions or measures. The trot 

 has but two measures. The animal raises a leg on each 

 side, in a cross direction, that is to say, the right fore-leg 

 with the left hind-leg, and so on. The canter has three 

 measures. After advancing the two fore-legs, one after the 

 other, the animal raises and brings forward the two hind-legs, 

 simultaneously. When this movement is greatly urged, 

 there are but two measures; the fore-limbs are raised to- 

 gether as well as the hind-legs ; it is then termed a gallop. 



189. LEAPING consists in a bending of all the limbs, fol- 

 lowed by a sudden extension of them, which throws the 

 body forwards with so much force as to raise it from the 

 ground, for an instant, to strike again at a certain distance in 

 advance. For this purpose, the animal always crouches 

 before leaping. Most animals make only an occasional use 

 of this mode of progression, when some obstacle is to be 

 surmounted ; but in a few instances, this is the habitual 

 mode. As the hind-legs are especially used in leaping, we 

 observe that all leaping animals have the posterior members 

 very much more robust than the anterior, as the frog, the 

 kangaroo, jerboa, and even the hare. Leaping is also com- 

 mon among certain birds, especially among the sparrows, 

 the thrushes, &c. Finally, there is also a large number of 

 leaping insects, such as the flea, the large tribe of grass- 

 hoppers and crickets, in which we find that pair of legs 

 with which leaping is accomplished much more developed 

 than the others. 



