Doctor Mitchell was born in Philadelphia in 1791, in which city for three generations his ancestors resided. He died in the same city May 13, 1865, in his seventy-fourth year, having heroically performed his duties as Professor almost up to the time of his death, although he was a constant sufferer from painful neuralgic disease of the stomach, at times almost unendurable. His early education was in Quaker schools, the best in those times in that city, and in the University of Pennsylvania. After a year spent in a drug store and chemical laboratory he became office pupil of the late Doctor Parrish, and, after attendance on three full courses of medical lectures in the Medical Department of the University, he graduated in medicine. His thesis "On Acidification and Combustion" was published in the Memoirs of the Columbian Medical Society. His mind and pen always in active operation, he published papers in _Coxe's Medical Museum_, _New York Medical Repository_, _Duane's Portfolio_, and other periodicals. Early in 1812, he was appointed Professor of Vegetable and Animal Physiology in Saint John's Lutheran College, and, in the following year, as Lazaretto Physician, which office he held for three years. In 1819, he published a duodecimo volume on Medical Chemistry. From 1822 to 1831, he was actively engaged in medical practice at Frankford, near Philadelphia. In 1826, he founded a Total Abstinence Temperance Society, to the tenets of which he rigidly adhered during the whole of his life, deprecating the use of alcohol, even in the preparation of the tinctures of the apothecary. He was also a strict Presbyterian. In 1826, the honorary degree of A. M. was conferred on him by the Trustees of Princeton College, New Jersey. In the winter of 1830-31, he was called to the chair of Chemistry in the Miami University, and in the following summer to the same chair in the Medical College of Ohio, at Cincinnati, which was soon thereafter amalgamated with the Miami School, where he remained until called to the same chair in the Medical Department of Transylvania University in 1837. He was transferred, as before mentioned, in the following year to the chair of Materia Medica, Doctor Peter having been called to that of Chemistry, etc. Here Doctor Mitchell continued until the end of the session of 1848-49. In the summer of 1847, the Philadelphia College of Medicine held its first session, and Doctor Mitchell filled in it the chair of Theory and Practice, Obstetrics, and Medical Jurisprudence. In March, 1849, resigning his chair in the Transylvania School, he joined himself with the Philadelphia College with a view to a permanent connection.