HAHNEMANN, SAMUEL CHRISTIAN FRIEDRICH (1755- 1843), the founder of the homoeopathic system of medicine, was born at Meissen in Saxony, 10th April 1755. He studied first at the "elector's school" of Meissen, and thereafter as a student of medicine at Leipsic and Vienna. He took the degree of M.D. at Erlangen in 1779, and after acting as physician at various places he returned in 1789 to Leipsic, where he largely occupied himself in the translation of medical works. While working at Cullen's ..4fateria .3.1ed•ica, he was struck by the contradictory account given of the properties of Peruvian bark. He had previously meditated much on the unsatisfactory nature of the science of medicine ; and, after much refiexion and many experiments, he became convinced of the truth of the principle sintilia similibetx curuntur (see HOMOEOPATHY), i.e., the cure for a disease is the very drug that would in a healthy person produce the symptoms of such disease. Further experiments convinced him that the conventional doses produced symptoms of unnecessary and dangerous violence, and this led to another principle, that of minimum doses, according to which the benefit to be derived from a medicine can be fully obtained by the administration of a very small quantity. Firmly convinced of the truth of these principles, Hahnemann spent the rest of his life in making them known to the world. He encountered much opposition, and in 1821 was forced to leave Leipsic, as he was not allowed to dispense his own prescriptions. The grand duke of Anhalt-Kothen, however, appointed him his physician, and at Kothen lie resided till 1835 when lie removed to Paris. He died 2d July 1843. Hahnemann was a man of remarkable courage and perseverance. He not only sacrificed his immediate interests for the sake of his convictions, but made many painful experiments upon his own person.

Halmemann's chief work, in which he expounds his system, is his Organon der rationellest Heilkunde (Dresden, 1810,; 6th ed., Kothen, 1865 ; English translation by Dudgeon, London, 1849). His other important writings are Pragnaelita de viribus snedicatnentorunt positivis (2 vols., Leipsic, 1805) ; Reine Arzneiniittellehre (6 vols., Dresden, 1811) ; Die ehrostisehen Krankheiten (4 vols., Dresden, 1828-30). His smaller writings have been edited by Staid (2 vols., Dresden and Leipsic, 1829-34). See also Albrescht's Hahnemann's Leben said Werken (2d ed., Leipsic, 1875).