REPAIR OF INJURY
Injury cannot always be avoided. Whether at the tenth or the ten thousandth stroke, the hammer eventually comes down on the thumb. The resulting injury brings a whole battery of repair mechanisms into play. Blood platelets secrete clotting factors that soon stem the bleeding, whether external or internal (in the form of a bruise). Other cells secrete a complex variety of substances that cause inflammation, thus raising the temperature of the tissue and making it harder for any invading bacteria to grow. They also keep the thumb
painful, thus protecting it from minor stresses that might disrupt the healing process. Simultaneously, the immune system rushes special- ized infection fighters to the site. They either attack any bacteria that the injury might have introduced or take them to lymph nodes, where they can be more easily destroyed. Fibrin strands link the tissues together, and, as healing proceeds, they slowly shrink and pull the sides of the wound together. Eventually nerves and blood vessels grow anew into the damaged tissue, and the hammering can proceed as before, albeit more cautiously. These repair processes show a precise, complex coordination that a symphony orchestra might well envy.
