Pierre Charles Alexandre Louis

Pierre-Charles-Alexandre Louis (14 April 178722 August 1872 ) was a French physician, clinician and pathologist known for his studies on tuberculosis, typhoid fever, and pneumonia, but Louis's greatest contribution to medicine was the development of the "numerical method", forerunner to epidemiology and the modern clinical trial, paving the path for evidence-based medicine.

Biography Louis was born in Ay, Champagne, the son of a wine merchant. He grew up during the French Revolution and initially thought to study law, later switching to medicine, graduating in 1813. His initial studies were in Reims, but he completed them in Paris. Louis also taught at the Pitié-Salpêtrière Hospital, also in Paris, and counted Oliver Wendell Holmes Sr. as one of his students.

Training After graduation, Louis accompanied the Compte de Saint-Priest, a family friend, to Russia, travelling with the Compte for several years before settling in the Ukrainian city of Odessa in 1816. He maintained a successful private practice for four years, receiving the honorary title of physician from the Tsar. Louis disagreed, publishing a paper in 1828 to that fact The "numerical method" involved the use of averages of groups of patients with the same illness to determine what should be done with individual cases of that illness. As part of the study, Louis emphasized the importance of the similarity of patients beyond mere disease, and attempted to account for factors such as age of patients in different treatment groups, diet, severity of illness and other treatments used beyond bloodletting. Louis also emphasized the importance of population (rather than individual) comparisons in the belief that differences between individual patients would "average out" in the group, though he failed to grasp the importance of randomization to ensure this. Opponents argued that individual cases were too diverse to be combined into statistically average groups; Louis responded by pointing out even individual cases have commonalities, and by claiming each case is unique, no progress could ever be made within medicine. Louis acknowledged his own research included too few cases for absolute certainty in the treatment methods, and his student later stated that once a total of 500 cases had been accumulated, then certainty could be reached.

Louis was mentor to Oliver Wendell Holmes Sr. during the younger man's training in Paris and strongly influenced his skeptical outlook.