134 



THE REASON WHY : 



The first point of shuth I coll 

 Lachesse, and is the chief of all, 

 And hath this property of kiade 

 To leven everything behinde." GOWER. 



411, From this structure the sloth 

 is entirely helpless on the ground ; but 

 among the branches of a tree, where it 

 catches by the feet, and suspends itself 

 without the least exertion or fatigue 

 this animal is as completely at home, 

 and as beautifully adapted to its place in 

 nature, as the fleetest creature -which 

 sports in the meadow, or bounds over 

 the heath. The sloth is decidedly the 

 best climber among mammals, though 

 upon the ground it is the worst walker. 



412. How is the supply of blood in the legs of climbing 

 animals specially regulated for the purpose ? 



In animals which are the best climbers and the worst walkers, 

 the arteries which supply the limbs with blood are divided into a 

 number of small branches, which branches are again united to form 

 the principal artery of the limb. This structure renders the circu- 

 lation in the limbs much slower than that in the body, and as both 

 the energy and exhaustion of an animal, or part of an animal, are 

 in proportion to the rapidity of the circulation, the legs of the sloth 

 and animals of a similar character, though moved with extreme 

 slowness, may be regarded as possessing greater power of endurance 

 than any other organs among vertebrated animals. 



413. In what respect is the form of the sloth remarkably 

 adapted to the localities which it inhabits ? 



Wherever the earth is green, there are browsing animals 

 appointed to consume the pasturage or the foliage, and to aid 

 the great scheme of nature in its successional changes. 



In the trophical forests, the green is not upon the surface of 

 :he ground, but upon the tops of trees ; and the browsing animals 

 destined to consume it, must have an inverted position to enable 

 them to make the foliage of the trees their pasture. 



A. pasture suspended in the air must have those which feed 



