MEMOIR OF ARISTOTI/E. 
105 
principles of classification seem to hare been almost 
as clearly understood in the age of Aristotle as it is in 
that of Boffon and Cuvier. It was not reasonable, 
indeed, to expect that, antecedently to the know- 
ledge of the circulation of the blood, of respiration, 
and 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 Stagirite 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 apartial 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 
