[On the 150th birthday of the internal medicine clinician Hermann Nothnagel (1841-1905)].

With respect to the present sub-specialization of several clinical specialties of the nineteenth century, the research work of Hermann Nothnagel is described as starting-point of cardiology, gastroenterology, clinical-experimental pharmacology and neurology. The most important topics of his main publications in these fields are enumerated chronologically in this brief presentation of his curriculum vitae. Emphasis is laid on the fact that in his person the variety of research is integrated to represent the unity of classic internal medicine. In 1901, as one of the founders of the "Gesellschaft für innere Medizin" in Vienna, Nothnagel helped to consolidate the independence of this new specialty, which at that time was a domain of general practitioners. In view of the enormous increase in knowledge nearly one century later, the mature branches have separated from the original trunk.