FIRST— THE ANIMAL KINGDOM. 



According to Cuvier, there are four principal forms, after which all living 

 beings seem to have been modelled. The basis of these distinctions is 

 laid in the organization of the creatures themselves. Sensation and move- 

 ment are the characteristics of animals. The heart and the organs of 

 circulation, seem a kind of centre for those functions which may be called 

 vegetative, while the brain and the nervous system, form the principal source 

 of the functions more exclusively animal. Descending from the higher to 

 the lower races of animals, both these systems are found gradually to 

 become more imperfect, and finally to disappear altogether. In the lowest 

 tribes in the scale, where nerves are no longer visible, the muscular fibre 

 also ceases to be distinct, and the organs of digestion are reduced to a 

 simple cavity in the homogeneous mass. In insects, the vascular system 

 disappears, even before the nervous system ; but in general, the dispersion 

 of the medullary masses is connected with the agents of muscular motion : 

 a spinal marrow, upon which knots, or ganglia, represent as many brains, 

 or seats of sensation, corresponding to the structure of a body divided into 

 numerous rings, and supported by pairs of limbs, distributed along these 

 annulations. This relative proportion in the structure of general forms, 

 which results from the arrangement of the organs of motion, from the dis- 

 tribution of the nervous masses, and from the energy of the circulating 

 system, constitutes the basis upon which M. Cuvier has founded the princi- 

 pal divisions of the Animal Kingdom. 



In the first of these general forms, which is that of Man, and the animals 

 which resemble him most nearly, the brain and the principal trunk of the 

 nervous system are inclosed in bony cases ; the first called the cranium, the 

 second the vertebrae. To the sides of the vertebral column, as to a centre, are 

 attached the ribs, and the bones of the members which form the frame-work 

 of the body. The muscles, in general, cover the bones, which they put into 

 action, and the viscera are inclosed in the head and trunk. Animals of this 

 form are called VePwTEBRATED Animals, {Aninmlia Vertchrata.) 



They have all red blood, a muscular heart, a mouth with two horizontal 

 jaws, distinct organs of vision, hearing, smell, and taste, situated in cavities 

 of the head, and never more than four limbs. The sexes are always 

 separate, and the distribution of the medullary masses and the principal 

 branches of the nervous system, is nearly the same in all. 



On a close examination of any of the characters of this leading division, 

 some analogy of conformation is always found, even in the species the most 



