Pierre Bretonneau (1778-1862)
French physician credited as one of the pioneers of modern medicine. He is known for identifying typhoid fever and naming diphtheria. He performed the first successful tracheotomy in 1825 and accurately distinguished scarlet fever from diphtheria in 1826. He studied disease in detail and was the first to think that disease was caused by bacteria – a hypothesis he could not confirm for lack of a microscope. He also discovered that the same illness could manifest itself differently in different patients.