Pierre Charles Alexandre Louis graduated from his medical course in Paris in 1813. He then travelled to Russia, where he practised medicine for seven years. A fatal diphtheria epidemic eventually convinced him of the inadequacy of his medical training and led him to abandon his foreign practice. He returned to Paris, where he resumed his training in the city’s hospital wards. Holding only hospital positions over the following decades, he became a successful teacher and diagnostician.
Louis has been described as the ‘inventor of the numerical method in medicine’. He distrusted theory and believed the truth in the medical cases he examined was in his observations, not in his judgments. A great supporter of observation in medicine, and not just textbook learning, Louis founded the Société d’Observation Medicale. He also became French medicine’s great systematiser. Rather than make original discoveries, he determined that conditions, such as typhoid fever, were specific diseases. He also argued that bleeding, one of the most common therapies of the day, was an ineffective form of medical treatment.
Louis was not the first clinician to use statistics in an effort to improve medical practice. He was, however, the first to make them the basis of medicine. He regarded the entire early tradition of medicine to be ‘imprecise’, and therefore worthless. Science, if it was to be reliable, had to be enumerated. He suggested that, previously, doctors had not counted, or had counted incorrectly. His quantitative approach gave his statements a finality and certainty never attained by doctors before. Popular with American students in France, Louis had a particularly strong impact on American medicine. He is now regarded as one of the founders of the idea of ‘evidence based’ medicine.