The Body: A Guide for Occupants

by Bill Bryson

‘Bone is stronger than reinforced concrete,’ says Ben, ‘yet light enough to allow us to sprint.’ All your bones together will weigh no more than about 20 pounds (nine kilograms), yet most can withstand up to a ton of compression. ‘Bone is also the only tissue in the body that doesn’t scar,’ Ben adds. ‘If you break your leg, after it heals you cannot tell where the break was. There’s no practical benefit to that. Bone just seems to want to be perfect.’ Even more remarkably, bone will grow back and fill a void. ‘You can take up to thirty centimetres of bone out of a leg, and with an external frame and a kind of stretcher you can have it grow back,’ Ben says. ‘Nothing else in the body will do that.’ Bone, in short, is amazingly dynamic.