MODES OF PROGRESSION. 67 



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

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

 ambling or pacing. 



188. RUNNING consists in the rapid repetition of the mo- 

 tions of walking. The running of lizards and birds is 

 merely an accelerated walk ; but in the horse and dog, 

 and most of the mammals, a distinction is made between the 

 walk, the trot, 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 gallop has three measures. After advancing the two 

 fore-legs, one after the other, the animal raises and brings 

 forward the two hind legs, simultaneously. Sometimes also, 

 when the gallop is greatly urged, there are but two mea- 

 sures ; the fore limbs are raised together, as well as the 

 hind legs. 



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 it 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 frogs, the kan- 

 garoos, jerboas, and even the hares. Leaping is also com- 

 mon among certain birds, especially among the sparro\vs, 

 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. 



