In 1967 cardiologists in Switzerland were struck by the sudden increase in the number of cases of so-called primary pulmonary hypertensive disease (PPHD). Up untill966, the cardiology centers in Switzerland had not seen more than one or two cases a year, but this number suddenly multiplied by ten or twenty times. At the June 1968 meeting ofthe Swiss Society of Cardiology, Gurtner et al. (1968b) presented a paper which raised the question whether the...