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- 
lowing passage, which appears intended to give the 
essential distinction of these four primary divisions : — 
“From all this result four different kinds of mction, 
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 all 
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 families as they are given in the Régne 
Animal ; the sub-genera and smaller divisions being 
omitted. 
