THE ANAT0]\f7 OF A BIRD 



17 



obvious perils to a nearly unique object. There are a good many 

 birds which do not, and some which cannot, fly. To the lirst cate- 

 gory belong such birds as the domestic ducks and fowls, and some 

 of the rails. These birds, when put to it — when chased by a dog, for 

 example — can often fly ; but as a rule they do not, or at most only 



P.m. 

 Fio. 11. — WiNO OF Adult Opisthocomus. (After Pyeraft in 

 •Natural Scienco.') 

 The hand is smaller relatively to the forearm ; c, the claw of digit I, much re<luced. 



flutter along. The Ostrich tribe and a few other birds have totally 

 lost the power of flight. But though this is the case, the bony 

 structure of the hand remains the same in the Ostrich and in the 

 American Ehea ; in the Cassowary, however, and the Apteryx of New 

 Zealand, the fingers are reduced to one. The last stage in the 

 atrophy of the organ of flight is seen in the giant and extuict birds 



MC.T 

 R. 

 I 



Mc.:ii. iiiic.m^-^-^- 



Fia. 12.— WiNQ OF Half-grown Ostrich. (After Parker.) 

 I, II, III, digits : R., U., D.c.f., carpal bones ; Mc, metacarpals. 



of New Zealand, the Moa or Dinornis, in which no trace of a wing has 

 been so far discovered. But in some of these birds in which the wing 

 is reduced in size, or so simplified in structure that it can no longer 

 serve its legitimate purpose, it is made use of for other purposes, 

 WTien the Ostrich skims along the surface of the sandy deserts 



