[Contribution to the history of endoscopy: improvements of Bozzini's light conductor by Johann Georg Ilg at the Vienna Jesophinian Medical-Surgical Academy].

One of the first "modern" endoscopes was the so called "light conductor" developed by Bozzini. In spite of repeated indications that certain modifications of this device had been carried out in the Josephinian Academy in Vienna in 1806 and 1807, no details were known on these improvements. With the discovery of the original report written by Dr. Johann Georg Ilg, who was prosector at the Josephinian Academy in Vienna at that time, an extensive description of this "Viennese model" and the performed changes is available for the first time. The detailed knowledge of these two early devices should now allow the identification and classification of both types of endoscopes in the context of the further development of endoscopy. This document of Ilg's report also reveals that the "modified light conductor" of Ilg ("Viennese model") already contains characteristics of endoscopes that first became available for clinical use in the second half of the 19th century.