THE VERTEBRAL COLUMN OF FISHES. 173 



but are large and strong in the carp ; to these 

 rib-bearing vertebrae the name of abdominal 

 has been given, -while the rest are termed 

 caudal. The bodies of the vertebrae are short, 

 and consequently the spine is made up of 

 numerous pieces, a circumstance which, con- 

 joined -with their mode of articulation, contri- 

 butes to its elasticity. If we look at a detached 

 vertebra, we shall find that at each end it is 

 hollowed out into a sort of cup-like cavity, or 

 a conical depression. In their natural situ- 

 ation, the edges of these cups are united by 

 a very elastic ligament, and the hollow part, 

 or double cone, (formed by the two cups joined 

 rim to rim,) if filled up with a highly elastic 

 glutinous substance, which allows not so much 

 a free play of one vertebra on another, as a 

 general mobility ; the extent of motion pos- 

 sessed by a single vertebra is multiplied in 

 the whole series forming the spine, the elastic 

 mobility of which, thus obtained, is very 

 considerable. When the vertebrae cease to be 

 put into motion, or bent by the action of the 

 muscles, the column I'esumes its Unear direc- 

 tion, the ligaments that unite the edges of the 

 cups, rendering it straight by an involuntary 

 contraction. It is evident, therefore, that the 



