Physiology of Penile Erection-A Brief History of the Scientific Understanding up till the Eighties of the 20th Century

Introduction. Understanding the physiology of penile erection is important for all who work in the field of sexual medicine. Aim. The aim of this study was to highlight and analyze historical aspects of the scientific understanding of penile erection. Methods. (i) Review of the chapters on the physiology of erection out of the author's collection of books dealing with male sexual functioning published in the German, French, Dutch, and English language in between 1780 and 1940. (ii) Review of the topic "physiology of penile erection" of relevant chapters of Classical writings on erectile dysfunction. An annotated collection of original texts from three millennia, including the study of all relevant references mentioned in these books. Main Outcome Measure. The main outcome measure used for the study was the scientific understanding of the physiology of penile erection. Results. In Antiquity, Galen considered penile erection as the result the accumulation of air. His ideas so dominated medieval medicine that nearly everyone then alive was a Galenist. The beginning of the Renaissance shows meaningful examples of experimental scientific work on the penis. Da Vinci correctly concluded that erections were caused by blood, and in the 18th century, Von Haller from Switzerland was the first who explained that erections were under the control of the nervous system. In the 19th century, a mindset that emphasized on experimentation determined a new direction, namely experimental physiology. Animal studies clarified that stimulation of the nervi erigentes-induced small muscle relaxation in the corpora cavernosa. Nearly all were published in the German language. That may be one of the reasons that the existence of the concept of smooth muscle relaxation remained controversial until the first World Congress on Impotence in 1984 in Paris. Conclusions. As the Renaissance's innovative research defined neural and vascular physiologic phenomena responsible for penile erection. The concepts from animal experimentations in Europe in the 19th century significantly contributed to the current understanding of penile erection