224 NATURAL THEOLOGY. 



a springiness to the whole column. Still ascend- 

 ing, we discover that the bony matter becomes 

 deposited between these cavities ; and here the 

 separate vertebrae first appear. If two vertebrae 

 of the great shark be taken out together, and the 

 sac between them punctured, such is tlie elasticity 

 of the walls of the sac, that the fluid will be 

 spouted out to a distance. In other fishes, as the 

 cod-fish, (an osseous fish,) the structure approaches 

 to that of the mammalia ; the intervertebral sub- 

 stance is gelatinous. In the whales, circular con- 

 centric ligaments join the vertebrae, and a small 

 portion in the centre consists of a glairy matter. 

 In mammalia, and in man, there are strong and 

 distinct bones of the vertebrae ; and these are 

 joined by a ligamentous cartilage, the outer circle 

 of which is remarkably strong, and the central 

 soft and elastic. The toughness and strength of 

 the exterior circle, and the soft condition of the 

 centre, make a joint equivalent in action to what 

 might be produced by a ball intervening between 

 the surfaces : a facility of motion is thus bestowed 

 which no form of solid could give ; and yet the 

 joint is so strong, that the bone breaks from vio- 

 lence, but the ligamentous cartilage never gives 

 way. When the veterinary surgeon casts a horse, 

 if he be not careful to restrain him, he will twist 

 himself with a force which will break the vertebrae. 

 It is a frequent accident in man ; but the texture 

 that gives mobility to the spine never yields. 

 The next thing admirable in the spine is the 



