Half Man, Half Bike: The Life of Eddy Merckx, Cycling's Greatest Champion by William Fotheringham:
Three days after the Giro, Merckx was in the Swiss town of Gippingen to start the second leg in a now-legendary triple: Giro, Tour of Switzerland and Tour de France, forty-three days of racing between 16 May and 21 July; three days recovery after the Giro, five between the finish of the Swiss Tour in the northwestern town of Olten and the Tour de France start in Brest. The ten-day Swiss event—the hardest stage race on the calendar behind the three Grand Tours—was won in essentially defensive style, in which Merckx landed the prologue time trial, then rode tactically until the final time trial to seal victory by fifty-eight seconds from the Swede Gosta Pettersson. But he came out of the race with a sore backside, a small sebaceous cyst precisely where his crutch sat on the point of the saddle. Watch the old television footage and it’s no surprise, given the way that The Cannibal throws himself around the bike as he chases Fuente through the mountains in the Giro. He was to have problems in this area for the next couple of years, like Louison Bobet, whose career was ended by a crutch wound.
The operation to clear up the cyst took place the day after the Tour of Switzerland finished, 22 June; recovery was expected to take five days, precisely the interval before the start of the Tour de France on Thursday 27 June. Merckx travelled to Brest for the Tour start a day late because he was having his stitches out. When the race started, the wound was small, but it was still open, which did not bode well for a three-week event. All he could do was pray for dry weather. As it was, he could never get comfortable, and the whole thing reawoke the referred pain in his left leg dating back to the crash in Blois. He won the prologue with his shorts bloodied as the wound opened further; for the next three weeks it needed constant care, constant bathing, the application of cream and sterile plasters, and cushioning with bits of foam and bandages.