498 THE MECHANICAL FUNCTIONS. 



gallops with the hinder : but this disadvantage 

 is amply compensated by its amazing swiftness 

 when running at full speed. 



Animals like the hare, in which, from the 

 great length of the hinder limbs, the posterior 

 half of the body is higher than the anterior, run 

 much better up a declivity than on level ground. 

 In a descent, on the contrary, they are obliged 

 to pursue an oblique and zig-zag course, other- 

 wise they would be in danger of oversetting, as 

 happens occasionally to the Agouti and the 

 Guinea pig, when these animals attempt to run 

 down hill. 



The Sloth, which is formed for clinging with 

 great tenacity to the boughs of trees, presents a 

 remarkable contrast to the animals we have just 

 noticed ; its fore legs being much longer than the 

 hinder, and its movements being proverbially 

 slow. The peculiar modifications of its mus- 

 cular powers are probably consequences of the 

 singular mode in which, as I shall afterwards 

 have occasion to notice, its arteries are dis- 

 tributed. 



The Cameleopard, likewise, has the fore legs 

 much longer than the hinder. The object of 

 this conformation was probably to elevate the 

 anterior part of the spine, so as to raise the head 

 as much as possible, and also to give a con- 

 siderable inclination to the whole column, for the 

 purpose of distributing more equally the weight 



