INTRODUCTION. 



Vertebrate, or Spini-cerebrata, that we are immediately concerned, inas- 

 much as it is that which includes the Mammalia, the class to which this 

 work is devoted. 



The vertebrate section (Vertebrata or Spini-cerebrata) of the animal 

 kingdom contains five great Classes, agreeing in the following particulars : 

 First, In the possession of a brain and a spinal chord (medulla spinalis), 

 conjointly enclosed in a cranium and vertebral column, whence emerges 

 a well-developed nervous system ; Secondly, In the possession of an 

 internal osseous fabric, or skeleton ; Thirdly, In the number of the limbs 

 never exceeding four ; Fourthly, In the possession of organs of vision, 

 hearing, smell, and taste ; Fifthly, In the mouth consisting of two jaws, 

 placed one above the other, and not on opposite sides ; Sixthly, In 

 the heart being muscular, and the blood red ; Seventhly, In the indi- 

 vidual distinctiveness of the sexes. 



These five classes are : I. Mammalia. II. Aves. III. Reptilia. 

 IV. Amphibia. V. Pisces.* 



* The arrangement of the animal kingdom by Dr. Grant, beginning from the lowest type of 

 organization, and proceeding to the highest, is exemplified in the following table : 



ANIMALIA. 

 I. Subregnum CYCLO-NEURA, or RADIATA. 



Classis 1. Polygastrica. (Infusory Animalcules, as Cercaria, &c.) 

 2. Porifera. (Sponges.) 

 3. Polypifera. (Zoophytes, as Gorgonia, Caryophyllia, Corals, Hydra, &c.) 



4. Acalephae. (Sea-nettles, Physalia, Beroe, Rhizostoma, Velella, &c.) 



5. Echinodermata. (Sea-stars, Echini, &c.) 



II. Subregnum DIPLO-NEURA, or ARTICULATA. 

 Classis 6. Entozoa. (Internal parasitic Worms.) 



7. Rotifera. (Wheel-like Animalcules, as Hydatina.) 



8. Cirrhopoda. (Barnacles, &c.) 



9. Annelida. (Leech, Nereis, Worm, &c.) 



10. Myriapoda. (Centipedes, &c.) 



11. Insecta. (Insects.) 



12. Arachnida. (Spiders.) 



13. Crustacea. (Crabs, Lobsters, Shrimps.) 



III. Subregnum CycLO-GANGLiATA, or MOLLUSCA. 

 Classis 14. Tunicata. (Pyrosoma, Cynthia, &c.) 



15. Conchifera. (Bivalve-shelled Molluscs, as Mussels, Oysters, &c.) 



16. Gasteropoda. (Slugs and Univalve-shelled Molluscs, as Snails, land or marine.) 



17. Pteropoda. (Clio borealis.) 



18. Cephalopoda. (Cuttle-fish.) 



IV. Subregnum SPINI-CEREBRATA, or VERTEBRATA. 

 Classis 19. Pisces. (Fishes. 



20. Amphibia. (Frogs, Newts, &c.) 



21. Reptilia. (Snakes, Lizards, &c.) 

 22 Aves. (Birds.) 



23. Mammalia. (Mammiferous animals.) 



Other Physiologists give a modification of this arrangement, separating into a fifth class termed 

 Acrita ("AKPITOS, confusus, o, non, and Kpivu, cerno), the Acalephce (or Sea-nettles), the Slerelmin- 

 tha (or solid intestinal worms with a parenchymatous structure), the Polypifera (or Zoophytes;, the 

 Porifera (or Sponges), and the Polygastrica (or infusory Animalcules), animals in which the nervous 



