12 THE REASON WHY": 



" If chance at length he find a srcensward smooth, 

 And faithful to the foot his spirits rise, 

 Ho cherups hri.sk his ear-erecting steed, 

 And -winds his way with pleasure and with ease." COWPER. 



634. Why are the ears of some animals turned forwards, and 

 those of others backwards? 



The external ears of beasts of prey, as lions, tigers, and wolves, 

 have their trumpet-part or concavity standing forward, to seize 

 the sounds which are before them namely, the sounds of the 

 animals which they pursue or watch. The ears of animals of flight 

 are turned backward, to give notice of the approach of an enemy 

 from behind, that he may not steal ' upon them unawares. 

 (See 392.) 



635. Why, in animals of great speed,- is the shoulder connected to 

 the trunk by the agency of muscles, and not by a collar-bone ? 



Because, if animals possessing great speed had been formed with 

 a collar-bone, it could not have withstood the shock from the 

 descent of the whole weight of the animal when thrown forwards ; 

 and even though the structure of the fore legs had been as powerful 

 as the posterior extremities, they would have suffered fracture or 

 dislocation. This beautiful provision not only serves to diminish 

 the shock of descending, but contributes to the elasticity of the 

 anterior extremities. 



636. Why are the knee-joints of the hind ley* of most swimming 

 animals turned round, as in a person who is knock-kneed ? 



Because by tnis mode of articulation the hind legs form a kind 

 of swimming sail ; and, in consequence of this they act more 

 horizontally, and thereby impel the animal forward in the water 

 with more velocity and with less exertion. 



637. Animals which are constructed principally for walking on the land make the 

 chief exertion with the fore feet when they swim ; and, therefore, they are sooner 

 fatigued than when they move even faster upon land ; hut quadruped animals 

 having a regular swimming habit, impel themselves chiefly by means of the hind 

 "eet, and on this account they are no more latigued in water than tbay are on Land, 



