272 THE ENGINES OF THE HUMAN BODY 



taught us to expect, may lead a quiet and useful life and 

 reach a good age. It will be seen from this how different 

 the conditions are under which the mechanic and physi- 

 cian carry out their office of mender. The mechanic is 

 an active agent ; the physician is Nature's oracle. 



On the road of life both motor vehicles and human 

 machines get damaged in collisions. Temporary repairs 

 have to be effected on the spot. The wooden spokes of 

 a smashed wheel may be temporarily replaced by splints 

 made from deal boards, thus making it possible for the 

 damaged vehicle to be taken to a repairing shop. The 

 driver himself may have a thigh-bone broken. Tempor- 

 ary splints are applied and he too is taken to a repairing 

 shop. But the manner in which the permanent repairs 

 are effected is totally different in the two cases. The 

 broken spokes of the wheel are replaced by new ones, 

 and although there are plenty of spare discarded parts of 

 the human machine to be had, they are of no use, for two 

 reasons : first, because they are dead ; and second, because 

 there are no standard sizes — no two human machines are 

 made exactly alike. The broken lever of the thigh has 

 to be welded by Nature, and it will take her six weeks or 

 more of steady application even if she is given the most 

 suitable conditions for her work. One thing Nature 

 cannot do ; if the broken ends are askew she cannot 

 straighten them out and restore the lever to its proper 

 shape. The surgeon has to perform this service for her. 

 The muscular engines of the thigh are torn and damaged 

 and have to be coerced by the surgeon before he can 

 replace the fragments into a good position. He may 

 even proceed as a carpenter does when he has to repair 

 the broken leg of a table — expose and brace the fractured 

 ends by plates of dead metal or of living bone. That, 

 however, is merely to hold the parts in position as Nature 

 welds them. She proceeds to work by stages ; the gap 

 between the broken ends is first filled by a temporary 

 scaffolding organised from the blood effused between the 

 broken ends ; then, very slowly, the bone-builders on 

 each side of the breach are roused to an activity by a 



