SPINE. 



A. Between all the twenty-four bones of the spine 

 there are springs introduced, of a substance resem- 

 bling gum elastic or Indian rubber. They are carti- 

 lages or gristles ; and may be seen to .perfection in a 

 loin of veal. They operate between the vertebrae 

 as so many spring cushions, so that, when we jump 

 or light heavily upon the ground, the violence of the 

 blow is in some measure broken by the spring, and 

 the jar is diminished upon the brain. " We can read- 

 ily understand," says Dr. Bell, "how great the influ- 

 ence of these twenty-four joinings must be in giving 

 elasticity to the whole column ; and how much this 

 tends to the protection of the brain. Were it not 

 for this interposition of elastic material, every motion 

 of the body would produce a jar to the delicate tex- 

 ture of the brain, and we should suffer almost as 

 much in alighting on our feet, as in falling on our 

 head." 



But there is another very curious provision for the 

 protection of the brain; the curved form of the spine, 

 which resembles an italic f. Elastic as this bone is, 

 yet if it were perfectly straight, a jar would have ex- 

 tended through it to the head with much more power. 

 Thus, if we should place a ball upon the end of a 

 long, straight spring of steel or whale-bone, and strike 

 the other end upon the ground, the ball would proba- 

 bly be shaken off by the concussion of the blow. But 

 if we first bend the spring in the shape of the letter/, 

 we should see the ball would not be jarred, but would 

 have an easy motion, like a bird rising and falling up- 

 on a bending branch. Thus admirably calculated is 



