A PERFECT LUBRICATING SYSTEM 87 



the grating in the articular plates and build wildly, 

 throwing out knarled outgrowths of bone round the 

 affected joint. With each movement a distinct creaking 

 sound can be heard. This is the condition which we 

 call chronic rheumatism ; it is a veritable " seizing " 

 of the joints, because the lubricant system has broken 

 down and we have not yet learned how to set it right 

 again. The fault lies with the cartilage-builders. They 

 grow as before and seek to make good the waste 

 that arises from wear, but fail us in their final sacrifice. 

 Instead of disappearing into oil, they turn to a stiff 

 leathery residue which clogs and wears the surfaces 

 of joints. 



In a motor cycle the movements of the piston-rod are 

 quite free ; it moves in air. But the piston cords of 

 muscular engines have to work amidst the pressure and 

 obstruction of surrounding tissues, and are thus exposed 

 to friction. Here again Nature shows her ingenuity. 

 Her handiwork is best studied at the wrist or ankle. 

 Around the wrist- and ankle-joints we can feel the 

 moving sinews or tendons of the muscles — often working 

 round sharp curves. In such positions piston cords are 

 made to work in lubricated tunnels. Not only is the 

 tunnel lined with a self-lubricating cover, but the surface 

 of the piston cord itself has a similar coating. Here 

 again we have moving surfaces separated by a fine 

 film of lubricant. The fingers and toes are tunnelled 

 for the passage of the tendons which work their triple 

 joints. 



The perfection of this lubricating mechanism lays the 

 human body open to certain dangers. Joint surfaces or 

 tendon sheaths, should they be injured or sprained or 

 should they be accidentally cut into, give disease-pro- 

 ducing germs gateways through which they may flood 

 the body. In such cases Nature usually responds by 

 closing up the avenues of access — obliterates the lubri- 

 cant spaces by sealing their opposed surfaces together. 

 Thus it comes about — as a sequel to infected wounds of 

 the hand or of the foot, or after severe sprains — that the 



