The diabetes-pancreas link
Who
Oskar Minkowski, a physiologist of Jewish descent, working with Joseph von Mering.
When
1889
Where
Strasbourg (then Germany)
In 1889 Oskar Minkowski and Joseph von Mering showed that removing a dog's pancreas caused diabetes, proving for the first time that the organ controls blood sugar. Minkowski, who came from a Jewish family, thereby opened the path that led decades later to the discovery of insulin.
Sources
Part of “The Gifts of the Jews” — verified Jewish contributions to the world, with sources.