Paul Ehrlich

Paul Ehrlich was a visionary German physician and scientist whose multidisciplinary innovations founded modern hematology, immunology, and chemotherapy. As a medical student fascinated by histology, Ehrlich discovered mast cells and developed differential dye-staining techniques using aniline dyes that enabled the classification of white blood cells, which Robert Koch used to identify the tuberculosis bacillus.

Turning to immunology, Ehrlich developed the first standardized diphtheria antiserum with Emil von Behring and formulated the side-chain theory of immunity, proposing that antibodies are specific cellular receptors triggered by toxins, earning the 1908 Nobel Prize in Physiology or Medicine. Ehrlich envisioned a synthetic chemical agent that would selectively target pathogenic invaders without harming host tissues—a concept he famously termed the 'magic bullet' (Zauberkugel). In 1909, after screening hundreds of organoarsenic compounds with Sahachiro Hata, he discovered Compound 606 (Salvarsan), the world's first effective chemotherapy cure for syphilis, ending centuries of terror.