THE FOUR CLASSES 1301 



THE FOUR CLASSES 



BARON CUVIER 



IF 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 accessory 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 modeled, 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 

 inclosed in a bony envelope, formed by the cranium 

 and vertebrae; to the sides of this intermedial column 

 are attached the ribs and bones of the limbs, which 

 form the framework of the body; the muscles gen- 

 erally cover the bones, whose motions they occasion, 

 while the viscera are contained within the head and 

 trunk. Animals of this form we shall denominate 

 Animalia Vertebrata. They have, all, red blood, a 

 muscular heart, a mouth furnished 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 dis- 



