or true Four-footed Beasts. 337 



the Linnsean method, formed chiefly on this principle, in 

 great measure superseded the respiratory classification, re- 

 commended by Aristotle, and adopted by Ray and others. 

 But the nervous system is the idol of the present day, and to 

 this the circulating seems doomed to yield as the respiratory 

 succumbed to it ; for, according to the developement and 

 concentration of the brain and nerves, a primary distribution 

 has been effected by the celebrated Cuvier, who divides the 

 whole animal reign into the vertebrate and invertebrate series; 

 the latter of which is again subdivided, before the distribution 

 of either into classes. Of the successive prevalence of these 

 several schemes, founded on the external or internal structure, 

 on the respiratory, the circulating and the sensorial systems, 

 more shall be said in a future essay ; the mere recollection of 

 their epochal predominance is all that will now be useful : 

 each plan has advantages and disadvantages peculiar to itself; 

 all assist in part to explicate the oracles of nature ; and it is 

 only when either becomes advanced unduly, that those sections 

 are rendered needlessly obscure, that its compeers are pro- 

 bably fitted to elucidate in turn. Therefore it is an object 

 worthy the attempt, so to reconcile the ancient emphatic 

 terms deduced from external and obvious characters, with the 

 internal and essential structure developed in modern times, 

 that while we retain, as far as possible, the familiar and expres- 

 sive nomenclature established by the one, the definitions may 

 be corrected to include the important anatomical discoveries 

 of the other. Thus, for example, while all the warm-blooded, 

 hairy, unfeathered brutes are known as beasts, and the cold- 

 blooded, lung-breathing animals are classed as reptiles, the 

 number and form of their limbs, and the popular epithets 

 derived therefrom, although arbitrary and erring as primary, 

 are most convenient and just as subordinate, distinctions ; and 

 the essential peculiarities of the intimate structure and consti- 

 tution of the separate grades is well predicated by calling the 

 four-footed beasts Quadrupeds, the four-footed reptiles Tetra- 

 pods ; thus making a single expressive word include, not only 

 the obvious external form, but also indicate the physiological 

 peculiarities of their internal structure. 



Great as are the varieties of external form, and numerous as 

 are the modifications of internal structure, still there is a rela- 



