The numbers invite awe: three billion beats in a lifetime; 100,000 miles of vessels. But on the hospital floor, wonder is often in short supply. Doctors forget how intimate their examinations and investigations can be. Stethoscope to chest. Order a blood test.

I remember on a morning ward round at medical school, our consultant wanted to check that the oximeter was working (a device which measures heart rate and blood oxygenation through the nail bed).