256 THE HOUSE. 



joint. Again, though the stifle joint is considerably bent, it is not 

 more so than the elbow joint, which will be clear on comparing 

 the two in the skeleton given at page 252. The chief disadvan- 

 tage sustained by the hind limbs as means of support will be found 

 in the hock, as compared with the knee, the latter being nearly 

 straight, while the former is much bent ; but as it has a long lever 

 to assist it (the os calcis), and as this is kept in position by the 

 powerful hamstring muscles, each of which serves its purpose far 

 more completely than the flexor of the carpus inserted in the os 

 pisiforme, it may readily be understood that the hind limb is not 

 greatly at a disadvantage in supporting the weight of the body. 



As agents op locomotion, 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 progression 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 ac- 

 tion 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 the feet under the belly ; and then suddenly ex- 

 tending them with the feet fixed in the ground, the weight is ne- 

 cessarily propelled. Or if the feet are 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 some- 

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

 which is the least amount of mischief to be apprehended from the 

 lull force of a lash out with the hinder limb. 



