Robert Koch, German bacteriologist, 19th century.

GERMANY - SEPTEMBER 09: Photogravure after a photograph by H Fechner. Koch (1843-1910) worked on anthrax which can be passed from cattle to humans. At the time anthrax was causing huge losses of cattle in France but, using a microscope, Koch found that the bacilli can form spores which are resistant to heat and drying. Koch isolated the anthrax bacillus from the blood of infected cows. Koch's pure cultures caused anthrax - the first time a laboratory culture was shown to cause disease. In 1882 Koch identified the tubercle bacillus which causes human tuberculosis, at the time responsible for one in seven of all European deaths. He won the 1905 Nobel Prize for his work on tuberculosis. From a collection of portraits of scientists published by Photographische Gesellschaft, Berlin, c 1910. (Photo by SSPL/Getty Images)