IN THE REPAIRING SHOPS 273 



mechanism which is not yet understood. The bone- 

 builders spread into the temporary scaffolding and replace 

 it in the course of a month by a rough and clumsy- 

 looking ferrule of imperfect bone. In six weeks or seven 

 muscular repairs have been effected and the bone ferrule 

 has become strong enough to allow the thigh to be used 

 lightly. It is only then, when the bone-builders become 

 subjected to the stresses which pass up the thigh in stand- 

 ing and walking, that they become engineers as well as 

 masons. As the thigh comes into use they rebuild and 

 trim the temporary ferrule of bone, replacing it with 

 properly designed props and struts to meet the strains 

 and stresses of normal usage. It is in this slow manner 

 that Nature welds the ends of a broken bone. The 

 surgeon's part is not that of a carpenter, but of a magis- 

 trate-policeman ; he has to see that the bone-builders are 

 not molested in any way whatsoever while in pursuit of 

 their lawful vocations. 



In the war motor vehicles as well as soldiers were 

 knocked out of action by enemy bullets. At the base, 

 well-equipped, extensive repairing sheds were erected 

 for mending the motor transport ; great hospitals were 

 fitted out for the repair of the wounded. No matter 

 how foul and infected the missile may have been which 

 damaged a vehicle, the hole was as easily patched as if it 

 had been perfectly clean. It was otherwise with wounded 

 human machines. Clean wounds, wounds which had 

 escaped infection by the germs of disease, healed kindly. 

 Nature healed them ; the surgeon had merely to serve 

 as Nature's watchman. But if they were infected, then 

 the surgeon had to come to Nature's aid. He had not 

 only to cleanse them ; he had actually to cut out the dead 

 and damaged tissues which afford disease-causing micro- 

 organisms the material on which they thrive best. Even 

 when the surgeon had done his utmost, infection some- 

 times got the upper hand, and the wound became the 

 seat of a furious battle. Nature has been so prudent 

 and far-seeing in designing her living machines that she 

 has provided them with a most elaborate mechanism, not 



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