THE ANIMAL KINGDOM 1? 



head and trunk. Animals of this form are called VEIITEB RAT- 

 ED ANIMALS, (Animalia Vertebrata.) 



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 remote from each other; and the grada- 

 tion of the same general plan is to be traced from Man down 

 to the lowest of the fishes. 



In the second conformation peculiar to animals there is no 

 internal frame-work or skeleton. The muscles are simply attach- 

 ed to the skin, which forms a soft and contractile covering, 

 from which proceed, in many species, stony plates or envelopes 

 denominated shells, of which the position and production are 

 analogous to that of the mucous body. The nervous system is 

 with the viscera included in this general covering, and is com- 

 posed of many scattered masses united by nervous threads. The 

 principal of these, placed upon the cesophagus, is denominated 

 the brain. Of the senses, properly so called, the organs of 

 taste and sight are alone to be distinguished, and even these 

 are sometimes wanting. One family alone exhibits the organs 

 of hearing. This division, however, is always characterized by 

 a complete circulating system, and particular organs for respira- 

 tion ; and the organs of digestion and secretion are little less 

 complicated than those of the vertebrated animals. Though 

 the general plan of their organization be riot so uniform in re- 

 gard to external configuration as the preceding division, yet 

 even between these parts there is always an analogous resem- 

 blance in structure and functions. This division is termed 

 MOLLUSCOUS ANIMALS, (Animalia Mollusca.j 



The third general form is that which is observed in insects, 

 worms, &c. Their nervous system consists in two long cords 

 extending along the belly, and swelled out at intervals into knots 

 or ganglia. The first of these, placed upon the oesophagus, though 



VOL. i. B 



