The paper discussed in this chapter was the first to compare some of the pharmacological effects of drugs to the effects induced by placebo treatments. It is one of the first studies to introduce the notion of a pharmacology of placebos, an idea which was quite unusual and innovative in the 1950s. In particular, in this study, many characteristics, which are typical of drug treatments, were investigated regarding placebo treatments. For example, peak effects, cumulative effects, carryover effects, and the relationship between efficacy and severity of disease were analysed in conditions such as post-partum pain. The main results show that placebos may produce effects that are similar to those induced by drugs. This pioneering study paved the way to a true biology of the placebo effect and to the modern emerging concept that placebos and therapeutic rituals use the same receptor and biochemical pathways that are used by drugs.