IRNICH W.: Georges Weiss' Fundamental Law of Electrostimulation Is 100 Years Old. In 1901, Georges Weiss published a voluminous paper that was the result of the charge by the Commission International du Parc-aux-Prince to investigate whether there are measures to make mutually comparable and to classify the different devices that physiologists used for nerve and muscle stimulation. Georges Weiss was born August 26, 1859 in Bischweiler (Alsace, France). He trained as an engineer in Paris and afterward began his medical training and received his medical doctorate in 1889. In the same year he was appointed “Professeur Agrègé,” and “Préparateur” at the Department of Medical Physics of the Medical Faculty at Paris. He made many contributions to physiology, but his main field of interest was electrophysiology. At the end of the nineteenth century the measuring capabilities for electrical stimulation pulses were limited and stimulation theories were based more on speculation than on measurements. Weiss found a fascinating method to produce short-lasting pulses of defined amplitude and duration. He constructed bridges by conducting threads within a circuit that were then destroyed by an air rifle bullet driven by liquid carbonic acid to produce short-lasting pulses. To investigate double pulses, the measuring system was expanded in the same manner, now with four bridging threads. The experiments were carried out with remarkable accuracy. The results included: (1) the threshold quantity that is the voltage-time-product, is a linear function of the pulse duration; (2) there is always a minimum of the delivered energy dependent on pulse duration; (3) pulse shape plays no role in electrostimulation. The physiologists were not so impressed by the Weiss report as it did not really meet the requirements as expressed by the title. There was no measuring technology available at that time to measure the quantity of devices with short-lasting pulses in the millisecond range. No wonder that the importance of the findings was not really perceived by the scientific community. It can be concluded that if there are statements in the literature contradicting one of the above three Weiss theorems, one can infer that the investigation is questionable.