30 INTRODUCTION. 
General distribution of the Animal Kingdom into Four Great 
Divisions. 
If, divesting ourselves of the prejudices founded on the 
divisions formerly admitted, we consider only the organization 
and nature of animals, without regard to their size, utility, 
the greater or less knowledge we have of them, and other ac- 
cessary circumstances, we shall find there are four principal 
forms, four general plans, if it may be so expressed, on which 
all animals seem to have been modelled, and whose ulterior 
divisions, whatever be the titles with which naturalists have 
decorated them, are merely slight modifications, founded on 
the development or addition of certain parts, which produce 
no essential change in the plan itself. 
In the first of these forms, which is that of man, and of the 
animals most nearly resembling him, the brain and principal 
trunk of the nervous system are enclosed in a bony envelope, 
formed by the cranium and vertebre; to the sides of this in- 
termedial column are attached the ribs, and bones of the 
limbs, which form the frame work of the body; the muscles 
generally cover the bones, whose motions they occasion, while 
the viscera are contained within the head and trunk. Ani- 
mals of this form we shall denominate 
Animalia Vertebrata. 
They have, all, red blood, a muscular heart, a mouth fur- 
nished with two jaws situated either above or before each 
other, distinct. organs of sight, hearing, smell and taste placed 
in the cavities of the face, never more than four limbs, the 
sexes always separated, and a very similar distribution of the 
medullary 1 mee and the principal branches of the nervous 
system. 1 Qs @ : 
Bya closer examination of each of the parts of this great 
series of animals, we always discover some analogy, even in, 
species the most remote from each. other and may trace the 
gradations of one same plan from man to the Jast of the fishes. 
In the second form there is no skeleton; the muscles are 
