Hans Christian Gram

Hans Christian Joachim Gram (1853 to 1938) was a Danish bacteriologist who developed the Gram stain, still a standard technique for sorting bacteria and viewing them under the microscope. The son of a professor of jurisprudence, he studied at the University of Copenhagen, worked early on botany and pharmacology, and began medical school in 1878, graduating in 1883. In Berlin in 1884 he devised the method that divides bacteria into two broad classes: those that hold the crystal violet stain and appear purple, now called Gram-positive, and those that take up the safranin counterstain and appear red, called Gram-negative. His first paper called the method imperfect and hoped others would find it useful. Gram also studied human red blood cells and was among the first to recognise that macrocytes are characteristic of pernicious anaemia. He became a professor of pharmacology in 1891, then professor of medicine in 1900, and retired in 1923. This record describes a historical scientist and is not medical advice.