CUVIERIAN SYSTEM. GENERAL DIVISIONS. 171 



" their double circulation, and by having the respira- 

 tory process simple, that is, performed by the lungs 

 alone. The quantity of their respiration is superior to 

 that of reptiles by reason of the form of their circu- 

 lating organ, and to that of fishes by the surrounding 

 element which they respire." The primary groups of 

 this anatomical system of Cuvier are, in fact, founded 

 upon motion and respiration, the external forms of the 

 creatures themselves not entering in the least degree 

 into his consideration. This is obvious from the fol- 

 loTfing passage, which appears intended to give the 

 essential distinction of these four primary divisions : — 

 " From all this result four different kinds of motion, 

 for which the four classes of vertebrated animals are 

 severally and exclusively designed. I. Quadrupeds, in 

 ■which the quantity of respiration is moderate, are formed 

 for walking and running, and their predominant charac- 

 teristic is vigour. II. Birds, whose respiration is greater, 

 possess the lightness and strength of muscles necessary 

 to support them in their airy flight. III. Reptiles, 

 which respire more freely, are doomed to creep upon 

 the earth, and many of them pass more or less of their 

 allotted period in a kind of stupor. Finally, IV. Fishes, 

 which move in a fluid almost as specifically heavy as 

 themselves, are enabled to execute their peculiar motions 

 by an arrangement altogether different from the rest." 

 This extract will sufficiently explain the nature of the 

 principles upon which this system is constructed ; prin- 

 ciples, indeed, of the utmost value, when properly used, 

 and combined with other considerations, but eminently 

 calculated — as the event, in the present case, has proved 

 — to substitute complex definitions for others which aU. 

 the world can see and understand. 



(224.) The Mammalia are arranged in orders, the 

 first of which implies that Man — essentially — is an 

 animal. The following table will show the ranks of the 

 chief groups or famihes as they are given in the Regne 

 Animal; the sub-genera and smaller divisions being 

 omitted. 



