OS ZOOLOGY. 103 



Of the necessity of such an arrangement, the 

 ancients, many of whose learned men were partial 

 to the study of natural history, were fully aware; 

 and we accordingly find that, Aristotle, the great 

 naturalist of former times, whose system of 

 zoology has been brought up to a late period, 

 divided animals first generally into viviparous or 

 those which produced at once living animals ; 

 and into oviparous, or such as produced eggs 

 from which their young were afterwards to be 

 excluded. And next particularly into classes 

 orders, and species, according to their external 

 form, to their food, their habits, and their habi- 

 tations. Of this very simple and natural system, 

 Aristotle was aware of the defects ; it being of 

 too general a nature to embrace under its respec- 

 tive heads all the several individuals, numerous 

 as they necessarily were, that required illustration. 

 He therefore recommended to future naturalists, 

 that, as the knowledge of anatomy advanced, 

 the particular structure of animals, internal as 

 well as external, should form the basis of their 

 improved systems of zoology. This classification, 

 however, continued until nearly the close of the 

 seventeenth century, when our celebrated coun- 

 tryman, Ray, availed himself of Aristotle's sug* 

 gestions ; and observing that the structure of the 

 lungs and heart varied in different animals, he 

 struck out a new arrangement, founded upon 

 the peculiarities of those organs; which took the 



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