3t)2 THE MECHANICAL FUNCTIONS. 



a well-marked division of Zoology, comprehend- 

 ing all the larger species that exist on the globe, 

 in whatever climate or element they may be 

 found ; and including man himself, placed, as he 

 unquestionably is, at the summit of the scale ; — 

 the undisputed Lord of the Creation. 



A remarkable affinity of structure prevails 

 throughout the whole of this extensive assem- 

 blage of beings. Whatever may be the size or 

 external form of these animals, whatever the 

 activity or sluggishness of their movements, 

 whether they be inhabitants of the land, the 

 waters, or the air, a striking similitude may be 

 traced both in the disposition of their vital organs, 

 and in the construction of the solid frame -work, 

 or skeleton, which sustains and protects their 

 fabric. The quadruped, the bird, the tortoise, 

 the serpent, and the fish, however they may 

 differ in subordinate details of organization, are 

 yet constructed upon one uniform principle, and 

 appear like varied copies from the same original 

 model. In no instance do they present struc- 

 tures which are altogether isolated, or can be 

 regarded as the results of separate and inde- 

 pendent formations. 



In proceeding from the contemplation of the 

 structures of articulated to those of vertebrated 

 animals, we appear to pass by a rapid excur- 

 sive flight, from one great continent to ano- 

 ther, separated by an immense gulf, contain- 



