MAMMIFEROUS ANIMALS. 91 



drag itself onward, by first extending the anterior legs, 

 and then bending them so as to draw the body after 

 them ; the hind legs affording but very little assist- 

 ance by their impulsion. It is this circuinstance 

 which renders the progression of the Sloths so labo- 

 rious. — Those animals which have their forelegs 

 very short in proportion to their hinder ones, would 

 be incapable of sufficiently supporting their bodies, 

 and must fall down forward on each impulse of the 

 latter, had they not the precaution to make a pranc- 

 ing movement ; that is, to raise the anterior extre- 

 mities entirely off the ground, previously to their 

 being impelled onward by means of the hind feet^ 

 Accordingly such animals cannot, in propriety of 

 language, be said to walk ; they only move forward 

 by leaps. This is the case with the Hares, the -Rats, 

 and particularly with the Jerboas and Kangurcos. 

 Indeed these animals cannot be said to walk at all, 

 except in the action of ascending. When they at- 

 tempt to walk slowly en level ground, they are oblig- 

 ed to move themselves by the fore feet, and merely 

 to drag after them the hind pair. This may be ob- 

 served in Rabbets. — When the hind feet are very 

 much separated, their impulse becomes more lateral. 

 It thence results that, at each step, the trunk is al- 

 ternately impelled side ways, and that the line of 

 motion becomes crooked. This may be remarked 

 in the swimming animals, whose manner of life re- 

 quires that there should be a considerable space be- 

 tween the hind legs ; such as the Otters, and the 

 Beavers. — Man^, anda certain numberof other animals 

 are capable of seizing objects^, by surrounding and 



