Why? The Science of Athletics

94 Bones Act as our Levers WHY?-THE SCIENCE OF ATHLETICS they have no actual power of leverage in themselves: They are, as one might say, inanimate objects which, when suitably actuated, supply the rigid strength to over- come a point of resistance. It has been shown already that a frame of cartilage precedes bone-formation in the case of an unborn child, and even after the bones are formed and _stabilized Nature leaves a certain amount of such cartilage unchanged for a definite and specific purpose. If Nature had so arranged things in the evolution of man that all the building-cartilage was to be turned into bone, none of our freely B comfortable movements would have been possible, because the ends of bones coming together would have grated and constant friction would so_on have worn away the substances. Nature, however, has provided her own process to prevent jarring and friction. A FIG. IO We have two hundred bones, two hundred and sixty pairs of muscles to move them, and two hundred and thirty joints to allow our bones to play upon each other. Over the end of each bone a layer of cartilage remains which is dense, wonderfully -elastic and acts both as a shock-absorb~r and a friction-pad. There is joint-lubri– cation by means of synovial fluid, which is an albuminous fluid secreated by membranes in the interior of joints and in other places needing lubrication. The manner in which the joints are formed · is, of itself, a matter of grea-t importance to the athlete. For example, the "ball and socket" arrangement of the hip joint shown in Fig. I I is a primary consideration with all hurdlers . ' In the old days, when athletes merely sailed over their hurdles, the possibility of making the hip more , mobile had not been taken into consideration. Then the whole theory of hurdling and the action of the rear