MEMOIR OF ARISTOTLE. 105 



principles of classification seem to have been almost 

 as clearly understood in the age of Aristotle as it is in 

 that of Buffon and Cuvier. It was not reasonable, 

 indeed, to expect that, antecedently to the know- 

 ledge of the circulation of the blood, of respiration, 

 .*nd also of the physiology of the absorbent and ner- 

 vous system, a natural classification could have been 

 accomplished on principles so satisfactory as has 

 been done by modern philosophy; yet on comparing 

 the zoology of the Slagirite with that of our times, 

 we discover that, even in the infancy of science, 

 there is frequently sufficient light, in the uniformity 

 of Nature's laws, to guide the mind in deducing ge- 

 ' neral conclusions from a systematic examination of 

 facts. The progress of knowledge has shewn the 

 existence of such a general coincidence and harmony 

 of relation between the several component parts of an 

 individual animal, that even a partial acquaintance with 

 the details of its structure will enable the inquirer to 

 ascertain its true place in the scale of organization ; 

 and hence, although Aristotle knew nothing of the 

 circulation of the blood, or of the general physiology 

 of the nervous system, and even comparatively little 

 of the osteology of animals, yet subsequent disco- 

 veries have scarcely disturbed the order of his ar- 

 rangement. He placed the whale, for instance, in 

 the same natural division with common quadrupeds, 

 because he saw that, like them, it is viviparous, 

 and suckles its young, and respires by lungs and 

 not by gills; and to this class it still belongs the 



