OF THE SPINE. 225 



manner in which the head is sustained on a column 

 possessing elasticity, and in which the brain is 

 thereby saved from undue concussion in the move- 

 ments of the body. This object is not attained 

 altogether through the elastic substance in the 

 spine which we have described ; but it is owing, 

 in a great measure, to the general form of the 

 spine in man. Had the vertebrae been built up, 

 like a lofty column, of portions put correctly and 

 vertically over one another, the spine would not 

 have had the advantages which result from the 

 structure that we have to describe. As the in- 

 cumbent weight would then have fallen on the 

 centres of all the bodies of the vertebrae, they 

 must have yielded in a slight degree only. Ac- 

 cordingly the figure of the italic / is given to the 

 column, which waving line we need not admire 

 because it is the line of beauty, as some have de- 

 fined it, but because it is the form of elasticity. 

 The spine being already in a curved shape, it 

 bends easily ; the pressure is directed upon the 

 margins of the vertebrae and of the intervertebral 

 substances, and they therefore yield readily ; and 

 by yielding, they produce an increase of the curve, 

 a consequent shortening of the whole column, and 

 admit an easy return to their original places. 

 Suppose we rest the palm of the hand upon 

 a walking-cane, which is elastic, but perfectly 

 straight ; it bears a considerable pressure without 

 yielding, and when it does yield, it is with a jerk; 

 but if it be previously bent, however we may in- 



