30 INTRODUCTION. 



General distribution of the Animal Kingdom into Four Great 



Divisions. 



Ifj 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 vertebrse ; 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 masses and the principal branches of the nervous 

 system. 



By a 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 last of the fishes. 



In the second form there is no skeleton ; the muscles are 



