Paul EhrlichThere have been two famous Dr. Paul Ehrlichs
A German, Paul Ehrlich (March 14, 1854-1915), won the 1908 Nobel Prize in physiology or medicine. He is noted for his work in hematology, immunology, and chemotherapy. He coined the phrases magic bullet, and chemotherapy. The idea of a magic bullet is also his.
The magic bullet concept comes from the experience of 19th century German chemists with selectively staining tissues for histological examination, and in particular, selectively staining bacteria (Ehrlich was an exceptionally gifted histological chemist, and invented the precursor technique to Gram staining bacteria). Ehrlich figured that if a compound could be made that selectively targeted a disease causing organism, then a toxin for that organism could be delivered along with the agent of selectivity. Hence, a "magic bullet" would be created that killed only the organism targeted.
A problem with the use of the magic bullet concept as it emerged from its histological roots is that people confused the dye with the agent of tissue selectivity and antibiotic activity. Prontosil, a sulfonamide, whose active component is sulfanilamide, is a classic example of the fact that color is not essential to antibiotic activity.