Compound monocular microscope, 1861-1870.
© Science Museum / Science & Society Picture Library
A bras microscope made by Nachet et Fils of Rue St Severin 17, Paris. This microscope is believed to have belonged to French chemist and father of modern bacteriology Louis Pasteur (1822-1895). Pasteur carried out experiments in the 1860s which proved that germs present in the air are responsible for disease and decay. He discovered a proces of heating liquids to kill pathogens in milk, wine and foods, now known as pasteurisation, and went on to produce vaccines against anthrax and rabies.