THE EXTREMITIES 353 



understood that the hind-limb is not greatly at a disadvantage in supporting 

 , the weight of the body. 



As AGENTS OF LOCOMOTiox, the offices of the fore and hind limbs are 

 widely different. Each has been already described as consisting of four 

 sections, bent at angles on each other. In the fore-limb these angles are 

 framed to serve as springs, so that when the feet touch the ground, they 

 are enabled to adapt themselves so as to avoid altering the line of progres don 

 of the body. In those animals which have small and short fore-legs, as the 

 kangaroo and hare, the most rapid locomotion ever consists in a series of 

 curves ; whereas, in the horse at full speed, the body progresses in one 

 straight line, owing to this elastic structure of the anterior limbs. So, also, 

 in descending from an extraordinary leap, the springy action of the fore- 

 limbs of the horse is so powerful that he can get off again without dwelling, 

 whereas the kangaroo and hare must depend almost entirely upon their hind- 

 legs, and consequently stop for a second after their descent. On the other 

 hand, the angular formation of the hind-limbs is intended to enable the 

 animal to drive its whole body forward, by first flexing all the joints, and 

 thus drawing their feet under the belly ; and then suddenly extending them 

 with the feet fixed on the ground, the weight is necessarily propelled. Or 

 if the feet ai-e not fixed they are lashed out backwards, developing the 

 action so well known as "kicking." The difference between the powers 

 displayed by the two limbs, in straightening their component parts, is well 

 displayed in comparing kicking with the striking out of the fore-foot, which 

 is common enough among vicious horses. It is true that the latter will 

 sometimes cause a severe blow ; but it could very rarely break a limb, which 

 is the least amount of mischief to be apprehended from the full force of a 

 lash out with the hinder-limb. 



