19th-century German physicians

Otto Michael Ludwig Leichtenstern (14 October 1845 – 23 February 1900) was a German internist born in Ingolstadt.
In 1869 he received his doctorate from the University of Munich, later working as an assistant of clinical medicine in Munich under Karl von Pfeufer (1806–1869) and Joseph von Lindwurm (1824–1874). After the death of Felix von Niemeyer (1820–1871), he served as interim head of the medical clinic in Tübingen prior to the appointment of Carl von Liebermeister (1833–1901) as Niemeyer's permanent replacement. Leichtenstern remained at the Tübingen clinic for several years, afterwards serving as head physician of internal medicine at the city hospital in Cologne (1879–1900).
Leichtenstern is remembered for publishing articles on almost every facet of medicine. In the field of helminthology, he made contributions in his investigations of hookworm (Ancylostoma duodenale).In 1898 he suspected that the compound 2-naphthylamine (2-NA) was involved in human bladder tumorigenesis. With Adolph Strümpell (1853–1925), the eponymous "Strümpell-Leichtenstern encephalitis" is named, a disease also known as acute hemorrhagic encephalitis.

Ferdinand Adolph Theophil Hueppe (24 August 1852 – 15 September 1938) was a German physician, bacteriologist and hygienist. From 1900 to 1904, he was the first Deutscher Fußball-Bund (DFB, German Football Association) president.

Franziska Tiburtius (24 January 1843 – 5 May 1927) was a German physician and advocate for women's education.

Josef, Baron von Mering (28 February 1849, in Cologne – 5 January 1908, at Halle an der Saale, Germany) was a German physician.
Working at the University of Strasbourg, Mering was the first person to discover (in conjunction with Oskar Minkowski) that one of the pancreatic functions is the production of insulin, a hormone which controls blood sugar levels.
Mering was curious about the pancreas, a comma shaped organ, situated between the stomach and the small intestine. In an effort to discover its function, he removed the organ from a dog. The dog was then noticed frequently urinating on the floor, although it was house trained. Mering realised that this was a symptom of diabetes and tested the urine, which was found to be high in sugar, confirming his suspicion.
Josef von Mering helped to discover barbiturates, a class of sedative drugs used for insomnia, epilepsy, anxiety, and anesthesia. In 1903, he published observations that barbital (then known as diethyl-barbituric acid) has sedative properties in humans. In 1904, he helped to launch barbital under the brand name Veronal. Veronal was the first commercially available barbiturate sedative in any country. Von Mering collaborated with the chemist Emil Fischer, who was also involved in the discovery of barbital.