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 married late in life, having a single son (Armand) who died of tuberculosis while still a boy in 1854, and Louis retired from medical practice the same year. The American politician Charles Sumner, who visited Louis and observed him teaching at the Hôtel-Dieu de Paris, described him as "a tall man, with a countenance that seems quite passive." 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. However, in 1820 an outbreak of diphtheria forced him to recognize the inadequacy of his medical knowledge. He returned to Paris where he worked, initially without pay, at a hospital for seven years, collecting the case histories of thousands of patients and performing hundreds of autopsies. He eventually wrote studies on the treatment of tuberculosis and typhoid fever, and produced the "numerical method" for evaluating the effectiveness of therapies. Numerical method Starting in 1823, Louis began publishing the results of his research on a variety of topics, numerically analyzing information gathered from his case studies and autopsies. In the 19th century, an influential theory was proposed by French physician François-Joseph-Victor Broussais, that fevers were the result of inflammation of the organs, and bloodletting was an effective treatment for any fever. Louis disagreed, publishing a paper in 1828 to that fact (expanded in 1834 to a book-length treatise in the American Journal of the Medical Sciences entitled "An essay on clinical instruction"), which demonstrated that the use of bloodletting for pneumonia was ineffective. Louis' approach was