108 NATURAL THEOLOGY. 



and to throw the change and the pressure pro- 

 duced by flexion almost entirely upon the inter-- 

 vening cartilages, the springiness and yielding 

 nature of whose substance admits of all the mo- 

 tion which is necessary to be performed upon 

 them, without any chasm being produced by a 

 separation of the parts. I say, of all the motion 

 which is necessary ; for although we bend our 

 backs to every degree almost of inclination, the 

 motion of each vertebrae is very small : such is 

 the advantage we receive from the chain being 

 composed of so many links, the spine of so many 

 bones. Had it consisted of three or four bones 

 only, in bending the body the spinal marrow must 

 have been bruised at every angle. The reader 

 need not be told that these intervening cartilages 

 are gristles, and he may see them in perfection in 

 a loin of veal. Their form also favours the same 

 intention. They are thicker before than behind ; 

 so that, when we stoop forward, the compressible 

 substance of the cartilage, yielding in its thicker 

 and anterior part to the force which squeezes it, 

 brings the surface of the adjoining vertebrae nearer 

 to the being parallel with one another than they 

 were before, instead of increasing the inclination 

 of their planes, which must have occasioned a 

 fissure or opening between them. Thirdly, for 

 the medullary canal giving out in its course, and 

 in a convenient order, a supply of nerves to dif- 

 ferent parts of the body, notches are made in the 

 upper and lower edge of every vertebrae, two on 



