Paul Trendelenburg was born in 1884 into a family with a strong medical background (Starke 1998, 2004). His father, Friedrich Trendelenburg, a surgeon, is still remembered for introducing the signs for diagnosing venous insufficiencies in the legs and paralysis of the gluteal muscle. Paul himself studied medicine in Grenoble, Switzerland, and then in Leipzig, Germany. In 1908, he joined the Pharmacology Department (“Pharmakologisches Institut”) in Freiburg, Germany, to work on his dissertation (Trendelenburg 1909) and his “Habilitation” (Trendelenburg 1912), both under the guidance of Walther Straub, who had founded the Department. It was in the subsequent years as “Privatdozent” in Freiburg that he carried out the study on the peristaltic reflex (Trendelenburg 1917) that is the object of this commemorative article. In those days, academic mobility was high in Europe. In 1918, Trendelenburg obtained his first post at the “Landesuniversitat” Dorpat, Estland (now Tartu, Estonia). In 1919 he moved to the chair in Rostock and, in 1923, was appointed chairman of the department where he had started, the Pharmakologisches Institut in Freiburg im Breisgau, succeeding Walther Straub. During that period, the Trendelenburg family, including four children, lived on the upper floor of the Institute while one of his many pupils, Edith Bulbring, used the darkroom, after work, as her study and bedroom. A close friendship developed and many times, the Trendelenburg children, in spite of their parents’ admonitions (“Edith has to learn!”), joyfully invaded her room (Bolton and Brading 1992). In 1927, Trendelenburg moved to the chair in Berlin where Bulbring joined him for some time, before fleeing the rising tide of National Socialism. It is moving to realise that many years later, after the war, Paul Trendelenburg’s son Ullrich met Edith Bulbring again in the Department of Pharmacology in Oxford, then led by Yoshua Burn, and that there Ullrich discovered the inhibitory effect of morphine on noradrenergic neurotransmission (U Trendelenburg 1957) just as, 50 years ago, his father Paul had discovered the inhibitory effect of morphine on the cholinergic neurotransmission in his peristaltic reflex study. Throughout these career moves, Paul Trendelenburg continued to work with brilliance. Having started on the pharmacology of smooth muscles, tracheal and intestinal, he moved on to endocrinology and developed bioassays to measure, for example, plasma levels of adrenaline. In particular, the posterior pituitary gland became his subject of interest and he and his colleagues determined that the compounds from that region that had an antidiuretic action and that stimulated the uterus were actually synthesised in the brain, paving the way for the revolutionary concept of neurosecretion. Paul Trendelenburg was not only a scientist but a teacher as well and concentrated especially on converting experimental evidence into therapeutic action and guidelines. In 1926 he published the first edition of his textbook on the clinical use of drugs (Trendelenburg 1926), which, after his death, went through seven editions by 1954. His philosophy was clearly spelled out in his preface: “It was the intent of the author, by choosing the important, and leaving out the less important or that which has not yet been sufficiently tested, to develop in future doctors their capacity for determining when therapeutic action is based on solid ground”. During his Freiburg and Berlin years, Paul Trendelenburg was suffering from tuberculosis. As described by a contemporary, at one of his last meetings, “weak and feverish (Trendelenburg) held his excellent, inspiring W. J. E. P. Lammers (*) . A. M. Lammers-van den Berg . J. F. B. Morrison Department of Physiology, Faculty of Medicine and Health Sciences, UAE University, P.O. Box 17666, Al Ain, United Arab Emirates e-mail: wlammers@smoothmap.org Tel.: +971-3-7137534 Fax: +971-3-7671966