276 ON THE CLASSES OF THE 



Hilaire has shown, not only the accessory parts and ap- 

 pendages of the vertebral column, but also the habits and 

 manner of life of the individual. The Bird for instance has 

 got its trunk, or that sternal apparatus which incloses all the 

 principal viscera of the body, suspended to the hinder 

 part of its vertebral column ; the mammiferous animal has 

 the same essential part attached to the middle of its spine, 

 whereas in fishes it is so far placed in front that the sternum 

 may be said to form part of the head. In other words, the 

 quadruped is essentially constructed upon a plan which is 

 intermediate between that of Birds and Fishes. For my 

 part, I can hardly conceive a more conclusive argument in 

 favour of the truth that Birds do not immediately separate 

 the Mammalia from Fishes. 



Of vertebrated animals the Mammalia and Jives, but 

 particularly the former, are the most perfectly organized, 

 so far as perfect organization relates to the acuteness of 

 the senses. But perhaps each of the five groups has its 

 own peculiar advantages, since the Reptilia seem to com- 

 prise the animals which are the most tenacious of life; Fishes, 

 those which are the longest lived ; and some of the Amphibia 

 are peculiarly gifted with the means of breathing either in 

 air or water. And the whole of the Vertebrata forms what 

 Cuvier calls a division, and is distinguished from all other 

 animals by the body and limbs being supported by an inter- 

 nal articulated skeleton. The nervous system of these ani- 

 mals is always more or less concentrated, appearing to be 

 altogether subservient to one great medullary mass, which 

 is contained in a bony case adapted for its reception, and 

 which is called the skull. One of the principal parts of the 

 nervous system is the spinal marrow, which is lodged in the 

 canal formed by the annular nature of the vertebrae which 



