(Revised/updated edition of the original 1965 essay) Discrimination of Birth Types challenges current thinking about the conquest of disease. The basic thesis rests on an unorthodox view of susceptibility to disease, a view based on the work of T. W. Less, a Scottish physician whose research and publications were defended by the British press and ignored by public health authorities. The implications are very clear - if the ideas and arguments in this essay are sound, then vast sums of money are being misspent on costly medical technologies which can only confuse, not cure.