ANIMAL KINGDOM. 265 



It is unnecessary here to describe creatures so well 

 snown as birds, the more especially when the place as- 

 signed to them by all naturalists between Mammalia and 

 Chelonians seems perfectly consonant with the harmony 

 of Nature. Suffice it, therefore, to say that this charming 

 group of animals has perhaps the greatest energy of re- 

 spiration which is known to exist, and moreover appears 

 to have the organs of sight more perfectly organized for 

 the purposes of vision than any other Vertebrata. Some 

 of them, as the Palmipedes, are also the most gifted with 

 the power of locomotion, since they command three ele- 

 ments, and can make way equally well on land, in the air, 

 or in water. With the exception of some insects, we are 

 acquainted with no other instance of this in Nature. In 

 many other respects, also, Birds seem to vie with or even 

 to excel the Mammalia; from which however they may 

 always be distinguished with ease, whether we attend to 

 their nervous system, their mode of reproduction, their 

 alimentary or secreting organs, or lastly those of locomo- 

 tion. The organs of sense however, excepting those of 

 sight, appear to be much more complex in structure among 

 the mammiferous animals than with birds, though indeed 

 these last are by no means deficient in the power of smell- 

 in^, and many are even remarkable for their strong sense 

 of odours. — It has been said, with great justice, by 

 M. Cuvier, that of all the classes of animals that of 

 Birds is the most strongly marked,— is that in which the 

 species resemble one another the most, and which is se- 

 parated from all others by the greatest interval. In the 

 present state of science it is, indeed, impossible to define 

 accurately how we are to quit Birds in order to enter 

 among the Mammalia; and it is right to observe that this 



