Pierre Charles Alexandre Louis, a French physician, born at Ai, department of Marne, in 1787, died in Paris in September, 1872. He received his degree of M. D. at Paris in 1813, and subsequently entered the hopital de la charite in that city, where he studied diagnosis and pathological anatomy. His first works, Recherches anatomico-pathologiques sur la phthisie (Paris, 1825), and Recherches sur la membrane muqueuse de l'estomac, etc. (1826; 2d ed., 1843), procured him admission to the academy of medicine. His reputation meanwhile rapidly increased, and his position as a pathologist was one of the most eminent in Paris. In 1828 he was a member of the medical commission sent to Gibraltar to examine into the causes and cure of yellow fever, and concurred in the report on the disease published in 1832. In 1854 he retired from practice, with the reputation of one of the first physicians in his peculiar department in Europe. He is particularly distinguished for having first brought prominently into notice the importance of medical statistics as a means of acquiring information as to the characters, causes, phenomena, and particularly the mortality of disease.
He declared that the impressions received by the individual practitioner from observing and recollecting isolated cases were often imperfect or deceptive; and that genuine and trustworthy knowledge could be gained in medicine only by counting a large number of similar cases, and recording accurately the proportion of those in which each particular symptom or event occurred. This was known as the numerical method, and has no doubt exerted a great and beneficial influence on modern scientific medicine. Among his remaining works are: Recherches sur la fievre typholde (2 vols., 1828; enlarged ed., 1841); Examen de l'Examen de Broussais (1834); and Recherches sur les effels de la saignee dans quelques maladies inflammatoires (1835). He also wrote a variety of memoirs and papers on medical subjects.