A GENERAL OUTLINE 



OF 



THE ANIMAL KINGDOM. 



CHAPTER I. 



ON CLASSIFICATION. 



(1). FROM the earliest periods to the present time, the great 

 desideratum in Zoology has been the establishment of some fun- 

 damental system of arrangement, which, being universal in its 

 application, should distribute the countless beings surrounding us 

 into natural groups or divisions, such as might be subdivided 

 into classes, orders, and genera, by obvious differences of structure 

 in the tribes composing them, and thus enable the Zoologist at 

 once to indicate the position which any unknown animal ought 

 to occupy in the scale of existence, and its relations with other 

 creatures. 



(2.) Aristotle, the father of our science, was the first who at- 

 tempted a scientific division of the animal world ; * the outlines 

 of his system were rude in proportion to the necessarily limited 

 knowledge at his disposal, although his efforts were gigantic, 

 and still excite our warmest admiration. This acute observer ad- 

 mitted but two great sections, in one or other of which all known 

 beings were included, the highest comprehending creatures pos- 

 sessed of blood, (i. e. red blood,) corresponding to the vertebrata 

 of modern authors ; the lowest embracing animals which in his view 

 were exsangueous, or provided with a colourless fluid instead of 

 blood, and corresponding to the invertebrata of more recent 

 Zoologists. 



(3.) Linnaeus, like Aristotle, selected the circulatory system as 



* Historia Animalium. 



