MAMMALIA. 481 



trees, as in the cameleopard, still this same con- 

 stant number is preserved in the vertebrae which 

 it contains. When the neck is long, each indi- 

 vidual vertebra must necessarily be lengthened 

 in the same proportion. Thus in the Cameleopard, 

 the vertebra? of the neck consist of seven very long 

 tubes, joined together endwise, with scarcely 

 any developement of spinous processes, lest they 

 should impede the bending of the neck. The 

 greatest contrast to this structure is met with in 

 the Dolphin, and other Cetacea, which present 

 externally no appearance whatever of a neck, 

 but whose skeleton exhibits cervical vertebras, 

 closely compressed together, and exceedingly 

 thin, arid most of them united together ;* every 

 bone, thus formed, however, retains the marks 

 of having originally consisted of separate ver- 

 tebrae ; and still, in this extreme case, the number 

 of primary pieces is constantly seven, f 



* In the cachalot, the whole of these seven vertebrae are 

 usually anchylosed into one bone. 



f The Bradypus tridactylus,or three toed sloth, was, till very 

 lately, thought to constitute a notable exception to this law, 

 being described as having nine, instead of seven, cervical ver- 

 tebrae. It is now found, however, that the two last of these 

 vertebrae, which appeared to be supernumerary, ought properly 

 to be classed among the dorsal vertebrae, of which they possess 

 the distinctive characters, not only from the form and size of 

 their transverse processes, but also from their having small bony 

 appendices, articulated with them by a regular joint at their 

 extremities, and corresponding exactly, both in shape and situa- 

 tion, to the ribs, of which they may, in fact, be considered as 



VOL. I. I I 



