Paul Ehrlich (March 14, 1854 - August 20, 1915) was a German scientist who won the 1908 Nobel Prize in Physiology or Medicine. He is noted for his work in hematology, immunology, and chemotherapy. Ehrlich predicted autoimmunity calling it "horror autotoxicus". He coined the term "chemotherapy" and popularized the concept of a "magic bullet". He is credited with the first empirical observation of the blood-brain barrier and the development of the first antibiotic drug in modern medicine.