LINNiEUS. 270 



tion being simply to offer a brief account of them, 

 omitting all that is not absolutely essential. It 

 ought to be understood, that the entire work is 

 merely an index or catalogue of the productions of 

 nature ; that it was obviously intended as such by 

 its author ; and that they who object to the Sys- 

 tema Naturae, because it contains nothing more 

 than characteristic notes methodically arranged, for- 

 get that Linnaeus never professed to give descrip- 

 tions in it. 



The natural division of animals, he says, is indi- 

 cated by their internal structure. This principle 

 his modern adversaries have chosen to overlook, as- 

 serting that his classification is founded on exter- 

 nal form. In some species the heart has two dis- 

 tinct cavities, and the blood is warm and red ; of 

 these some are viviparous, — the mammalia, — others 

 oviparous, — the class oi birds. In certain species the 

 heart has only a single cavity, with a single auricle, 

 the blood red but cold ; of these the amphibia have 

 a voluntary respiration, y^\\\\e fishes respire by gills. 

 In other animals the heart has also a single cavity, 

 but without an auricle, while the blood is cold and 

 of a white t;olour ; of these the insects are charac- 

 terized by their antennae, the vermes or worms by 

 their tentacula. 



The Mammalia, which constitute the first class, 

 are the only animals furnished with teats. Their 

 clothing, hoofs, claws, horns, teeth, and other or- 

 gans, are briefly described, in such a manner as to 

 enable the student to comprehend the meaning of 

 the terms to be subsequently employed. The cha- 

 racters of the orders are derived principally from 

 the teeth. 



