On the first day of June, 1972, I was taught how to percuss the body. That night, lying flat on my back, the sheets pulled away and the lights off, I started just above my right lung, high, at the level of my nipple, pressing the middle finger of my left hand against my skin. I cocked my right wrist and let the fingertips fall like piano hammers: thoom, thoom.

‘Resonance!’ I said to myself, picturing the air vibrating in a million air sacs, a million tiny tambours.

I moved down an inch: thoom, thoom. Further down and further still, and then suddenly, thunk! thunk! – dullness. I had reached my liver, airless and solid.