A week-long investigation into the history and importance of five machines which changed the face of modern medicine, presented by Dr Mark Porter. 1: The Dialysis Machine. The invention of the "artificial kidney" meant that patients with renal failure had a good chance of survival by dialysis. But the early types were cumbersome and had to be largely built by the patients themselves. What was it like constructing membranes out of sausage skins and how does it feel to have to spend long hours on dialysis today? Producer Emma Kingsley Dr Mark Porter on x-rays: page 23