276 ON THE CLASSES OF THE 



Hjlaire 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 

 qviadruped is essentially constructed upon a plan which is 

 intermediate bptween that of Birds and Fishes. ' For iiiy 

 part, I can.hardly conceive a more conclusive argument in 

 favour of the truth that Birds dp not immediately separate 

 thp^ Mammalia from Yishes. r , . . " , , , v'- "f 

 ,, Or vertebra ted animals „theiVfa/7imaZza and ^ives, but 

 particularly the former, are the most perfectly organized, 

 so far as perfect, orgahization relates to thp acuteness of 

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

 pvi^n peculiar advantages, since ^he JReptilia seem to com- 

 prise the axiimals which are thejnost tenacious of life ; Fishes, 

 tl>ose which are the longest lived ; and some of the Amphibia 

 ^VG, peculiarly gifted with4he means of breathing either in 

 :^ir or water. And the whole of the Fier^eiraf a forms what 

 Cuvier calls a division, and is distinguished from all other 

 ^.nimals by the body and Umbs being supported by an inter- 

 nal articulated skeleton. The nervous system of these ani- 

 inals is always mpre or less concentrated, a,ppearing to be 

 altogether subservient tp one great medullary mass, \vrhich 



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

 whiphjs called, the s^cull.. One of the principal parts of the 



r.. nervous systeipistbe spinal marrow, whicl\ is lodged in the 

 :panal forjae4 by J^, anr^ijlaf |i?i!ture pf the, vertebi'aB^ wh,ich 



