William Osier became interested in descriptive biology as a schoolboy. His father was a priest, and his early university education emphasized the classics. After graduating in medicine, he taught in Canada and developed a close lifelong paternal relationship with William Francis, the son of a cousin. His practice was minimal in Montreal, Philadelphia, and Baltimore until his marriage to Grace Revere Gross. They married within months of publication of his textbook. Office practice and other consultations then generated substantial income. The pressures of practice and professional activities led to a move to Oxford, England, in hope of a more leisurely life. The Osler's home, The Open Arms, was a center of intellectual and social activity. Practice diminished, but fees increased. When World War I broke out, Sir William and Lady Osier actively joined the war effort. When their only surviving son, Revere, was killed in action, his death devastated both parents.