522 THE MECHANICAL FUNCTIONS. 



The clavicles do not reach the sternum, nor even 

 meet at the anterior jDart of the chest to form the 

 furcnlar hone ; for as the wings are not employed 

 in flying, the usual office of that bone is not 

 wanted. The form of the pelvis is different from 

 the ordinary structure ; for the pubic bones, which 

 in all other birds are separated by an interval, 

 here unite as they do in quadrupeds. 



The feathers are unprovided with that elaborate 

 apparatus of crotchets and fibres, which are uni- 

 versally met with in birds that fly. The filaments 

 of the ostrich's feathers, in consequence of having 

 none of these fibrils, hang loose and detached from 

 one another, forming the fine hair or down, which, 

 however ornamental as an article of dress, must 

 be viewed, w hen considered physiologically, as a 

 species of degeneracy in the structure of feathers. 



The Penguin, in like manner, has a wing, which 

 is, by its shortness, totally unfitted for raising the 

 body in the air : it has, indeed, received a very 

 different destination, being formed for swimming. 

 In external form it resembles the anterior extremity 

 of the turtle; but still we find it constructed on the 

 model of the wings of birds; as if nature had 

 bound herself by a law not to depart from the 

 standard of organization, although the purpose of 

 the structure is altogether changed. As penguins 

 are intended for a maritime life, all their extremities 

 are formed for swimming. Their legs are exceed- 

 ingly short, and placed far backwards ; so that 

 these birds are compelled, when resting on their 

 feet on the shore, to raise their bodies in a perpen- 

 dicular attitude, in order to place the centre of 

 gravity immediately above the base of support; a 



