76 VERTEBRATED ANIMALS. 



refined developements in her system of organization ; 

 resorting to new models of structure on a scale of 

 greater magnitude than before ; devising new plans of 

 economy, calculated for more extended periods of du- 

 ration ; and adopting new arrangements of organs, 

 fitted for the exercise of a higher order of faculties. 



The result of these more elaborate constructions is 

 seen in the vast series of Vertebrated Animals, which 

 comprises a well-marked division in Zoology, compre- 

 hending 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 through- 

 out the whole of this extensive assemblage of beings, 

 Whatever may be the size, or external form of these 

 animals, whatever the activity, or sluggishness of their 

 movements, whether inhabitants of the land or water, 

 or the air, a striking similitude may be traced in the dis- 

 position of their vital organs, and in the construction of 

 their solid frame works or skeletons, which sustains and 

 protects their fabric. The Quadruped, the Bird, the 

 Tortoise, the Serpent, the Fish, however they may differ 

 in subordinate details of organization, yet are constructed 

 upon one uniform principle, and appear like varied copies 

 from the same original model. In no instance do they 

 present structures, which are altogether isolated, or can 

 be regarded as the results of separate and independent 

 formations." 



Animals resist both heat and cold. But although there 

 is a general analogy with respect to the skeletons of all ver- 

 tebrated animals, and a general similitude in the disposi- 

 tion and construction of their vital parts, still there is a stri- 

 king and wonderful difference in the effects produced by 

 the action of these parts, especially vital action, on the 

 animal, and particularly on its temperature ; for while the 



What is said concerning the affinity of structure, which exists among 

 all animals with back bones 1 What is said of the different effects of 

 vital action on different vertebrated animals ? 



