Paul Ehrlich (1854-1915) was a pioneer of haematology and immunology. Graduating from Leipzig in 1878, Ehrlich discovered the mast cells in blood and techniques of differential staining, identified the other white cells of the blood, established the diazo reaction in the urine of typhoid patients, and the acid-fast staining reactions of the tubercle bacillus. In 1890 Robert Koch (1843-1910) the bacteriologist, invited him to the Institute for Infectious Diseases where he worked on immunity. His investigation of syphilis resulted in the discovery of the first two specific chemotherapeutic agents, salvarsan and neosalvarsan.
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