,1V PREFACE. 



which are commonly directed forwards, and 

 one backwards; but in some birds there are 

 only two toes, and in some only three. All 

 the bones in birds are much lighter, or fur- 

 nished with a larger cavity than in qua- 

 drupeds. 



With respect to the definition of a Bird, 

 as absolutely distinguished from all other 

 animals, it would be sufficient to say, accord- 

 ing to the old mode, that a Bird is a two- 

 footed, feathered animal. The power of 

 flight need not enter into the definition ; for 

 there are many birds which are perfectly 

 destitute of the power of flight; as the 

 Ostrich, the Cassowary, all the Penguins, and 

 some other birds. The feathers with which 

 birds are covered are analogous in their na- 

 ture to the hair of quadrupeds, being com- 

 posed of a similar substance appearing in a 

 dissimilar form. Beneath or under the com- 

 mon feathers or general plumage the skin in 

 birds is immediately covered with a much 

 finer or softer feathery substance, called down. 

 The external or common feathers are called 

 by different names on different parts of the 

 animal. The longest of the wing-feathers, 

 which are generally ten in number in each 



