OF THE SPINE. 223 



diflferent offices are performed by the construction 

 of this column ; how nature has established the 

 most opposite and inconsistent functions in one 

 set of bones ; — for these bones are so strong as 

 not to suffer under the longest fatigue or the great- 

 est weight which the limbs can bear ; and so flex- 

 ible, as to perform the chief turnings and bendings 

 of the body ; and yet so steady withal, as to con- 

 tain and defend the most material and the most 

 delicate part of the nervous system. 



In some animals, the lowest of the vertebrata, 

 the protecting texture of the spinal marrow hardly 

 deserves the name of vertebral column. In cer- 

 tain fishes,* for example, the spine consists of a 

 cartilage made tough by ligamentous intertexture. 

 In the myxine, this cartilage does not entirely 

 enclose the spinal marrow ; for it Hes in a deep 

 groove on the upper part of the spine. But let us 

 not suppose that in fishes there is any imperfec- 

 tion in the vertebral column : it is an elastic co- 

 lumn, on which the muscles act so as to become 

 the means of powerful locomotion; and in all 

 fishes the spine has, more or less, this remarkable 

 elasticity. Ascending in the scale of animals, we 

 find the cartilage forming the spinal column sub- 

 divided by cavities which contain a gelatinous 

 fluid; and these cavities, being surrounded with a 

 strong but elastic ligamentous covering, nothing 

 can be conceived more admirably adapted to give 



* Myxine, lamprey, sturgeon, &c. 



