John Crawford (3 May 1746 – 9 May 1813), an introducer of vaccination into America and investigator into the cause of disease, was born in the north of Ireland May 3, 1746. He was the second of four sons of a Protestant clergyman, all of whom became professional men, his brother Adair being physician to St. Thomas' Hospital, London, and professor of chemistry at Woolwich. At seventeen he entered Trinity College Dublin, and afterwards went to the Leyden University, where he graduated M. D. He then made two voyages to the East Indies as surgeon in the East India Company's service. About 1778 he was married and shortly after received an appointment as surgeon to the Naval Hospital on the Island of Barbadoes, a position of great responsibility. In 1780 a terrible hurricane devastated the island, where upon he furnished aid and medicines to the afflicted inhabitants without stint and without compensation. In 1781 he returned to England on account of bad health and during the voyage lost his wife. In 1790 he received from the Dutch government the appointment of surgeon-major to the colony of Demerara in South America; there he had charge of a military hospital of sixty to eighty beds. In 1796 he went to Baltimore. Here he helped forward the founding of the Baltimore General Dispensary, 1801; the penitentiary, 1802; the Bible Society, and the Baltimore Library. He delivered courses on natural history at the College of Medicine in 1811 and 1812, and his introductory lecture on “The Cause, Seat and Cure of Diseases” is extant. He held high rank in his profession, being censor, examiner, orator, and member of the committee to publish the Transactions of the Medical and Chirurgical Faculty, and consulting physician to the Board of Health and City Hospital. He was among the first in America to use vaccine virus, which he did in the summer of 1800, a date contemporaneous with that of its use by Dr. Waterhouse, of Massachusetts, who has been given the credit of its first use in the Western Hemisphere. He wrote many medical articles of great interest and value in the medical journals of the day. What most rivets attention on John Crawford is his remarkable research into the cause of disease. As early as 1790 he conceived—entirely independently—the idea of a living contagium—minute animalcula gaining access to the human body and there depositing germs to