HOW THE BACKBONE IS BALANCED 23 



they are never pulled apart however severe the accident. 

 The buffer or disc set between the vertebrae is made like 

 a water-cushion. Its centre is pulpy and springy, while 

 the surrounding cover, which also binds the vertebrae 

 together, is very strong. We all know how rough it is 

 to ride in a farm cart, and how smoothly a journey goes 

 in a good motor car ; the difference is due to the fact 

 that the farm cart has no springs or buffers. If it were 

 not for the intervertebral disc our journey through life 

 would be like riding in a farm cart. It is because of 

 these discs or buffers that we do not feel a jar with each 

 step, or do a damage to our bodies when we take a 

 high jump. The human machine, particularly the back- 

 bone, has been so skilfully cushioned or buffered that we 

 can walk, run, or jump on the hardest and roughest roads, 

 and yet its most delicate parts suffer neither discomfort 

 nor damage. 



Now, when we walk, these twenty-four blocks or 

 vertebrae have to be kept balanced, one upon the other. 

 During each step the poise of the body is being altered, 

 and the column of vertebrae would fall to one side or the 

 other if we had no means of keeping them rightly poised. 

 For that purpose a very great number of muscular engines 

 are provided which can turn the backbone in this direction 

 or in that, just as is required to keep our bodies upright. 

 In order that the vertebrae may be moved with ease and 

 precision they have been furnished with levers or pro- 

 cesses, and these the muscular engines use as crank-pins. 

 Each vertebra has a hinder lever or spinous process 

 (fig. 3) so that when the spinal column threatens to fall 

 forwards muscles attached to these processes are able to 

 bring it back into the erect position. By means of this 

 lever a vertebra can be partly turned or twisted. The 

 column might tend to fall to the right or to the left side ; 

 each vertebra is accordingly provided with a right and 

 left lever or transverse process ; each of these side levers 

 is moved by special muscles. Or the tendency might be 

 for the spine to fall backwards ; that danger is provided 

 against by very long levers which are called ribs. We 



