William Osler, one of the most influential and beloved physicians of all time, was born July 12, 1849, in a Canadian frontier hamlet called Bond Head, about forty miles north of Toronto. His parents, the Reverend Featherstone Lake Osler and Ellen Free Pickton Osler, were Anglican missionaries who emigrated from England in 1837. "Willie" was the eighth of their nine children, and the fourth son. For the first twenty years of his ministry, Reverend Osler's flock was some two thousand settlers, dispersed over about 240 square miles. Besides his church at Bond Head, the Reverend took care of several other small settlements, riding many miles on horseback each year. He and his wife, along with the older children, also tended a small farm attached to the parsonage. In 1857, when Willie was eight years old, his father requested a transfer, and was given the rectorship of Dundas, west of Toronto. Osler's parents were well-educated, hardworking, and devout, yet loving and playful with their children.

Willie Osler was an outgoing, athletic child, good at his studies, but with a penchant for elaborate practical jokes that would persist all his life. In grammar school, for example, he and his cohorts at various times locked a flock of geese in the schoolroom, removed all the desks and benches from a classroom, and shouted rude remarks at the headmaster through a keyhole. One year, these antics got Osler expelled briefly. In 1866, at the age of sixteen, he enrolled at the Trinity College School in Weston. The pranks continued, culminating in the tormenting of the school's unpopular matron, for which the boys were arrested and charged with assault. Osler's parents issued worried reprimands; feeling repentant, he announced that he would train for the ministry, though this was not a choice urged by either parent.

Osler's path turned in a very different direction, however, when the founder and warden of Trinity College School, the Reverend William Arthur Johnson, introduced him to natural history. Johnson became Osler's earliest scientific mentor, opening up a world refreshingly different from the standard curriculum of Greek and Latin classics. Fifty years later, Osler would still describe the experience vividly:

Johnson was, Osler recalled, "a good field botanist, a practical paleontologist, [and] an ardent microscopist" with a "rare gift for imparting knowledge and inspiring enthusiasm." With Johnson's guidance, Osler soon developed a passion for natural science. He became skilled at searching out, observing, and classifying all sorts of specimens in the Ontario woods and fields. He also became proficient with the microscope--not yet a commonplace tool--and familiar with the works of Lyell, Hunter, and Huxley in Johnson's library. For years, he made studies of diatoms (a type of algae) and polyzoa (microscopic invertebrates) he found in local rivers and ponds, and his first appearances in print, several years before he finished medical school, described some of this work.

Despite his affinity for natural history, Osler started studying for the ministry at University of Trinity College in Toronto in 1867, as he had planned. His courses, which included Algebra, Euclid, Greek, the Catechism, Latin Prose, and Roman History, seemed "dry crusts" after a diet of natural studies. To relieve the tedium, Osler spent much of his time reading science and visiting with Dr. James Bovell, a fellow naturalist and good friend of Reverend Johnson. Bovell, one of the best-educated physicians in Toronto, taught physiology and pathology at Trinity, and at the Toronto School of Medicine. Osler was soon attending Bovell's medical lectures, and found it an easy step "from the study of nature to the study of man," as he later said. Early in his second year at Trinity, he abandoned his theological studies and joined Bovell at the medical school. For the next two years, he worked constantly with Bovell and had free access to his mentor's fine medical library.

When Bovell left Canada in 1870 to return to his native West Indies, he advised Osler to finish his medical education at the McGill University Faculty of Medicine in Montreal. McGill's program had much higher standards than other North American schools of that era, and far greater opportunity for anatomical and hospital ward work. Osler attended lectures, worked as a clinical clerk and surgical assistant, and wrote up cases for presentation. Unlike many of his colleagues, he also carried out many post-mortem exams and developed a sound knowledge of pathology.

Osler received his MD and CM (Chirurgiae Magister or Master of Surgery) from McGill in 1872. He then went abroad for two years to pursue further training in physiology and pathology, and to get more clinical experience. (No such opportunities existed in North America at the time.) He studied in London for over a year, mainly with experimental physiologist John Burdon Sanderson, and made one of the first observations of blood platelets. From England he went on to Berlin, where he worked with eminent pathologist Rudolf Virchow. He finished his postgraduate tour with four months of classes and ward rounds at Vienna's large general hospital.

Returning to Montreal in 1874, Osler accepted a post as Lecturer in "Institutes of Medicine" at McGill, and was soon promoted to professor. Before the end of his second year, he had introduced new courses in histology and pathology. He and his pathology students volunteered to do all the autopsies at Montreal General Hospital, and were soon generating careful post-mortem reports on a wide variety of cases. He rapidly became one of the most popular faculty members--not just for his innovative teaching, but for his cheerful manner and enthusiasm for all aspects of medical study. Osler was also the sole attending physician to a temporary smallpox ward at Montreal General, and taught pathology for the Montreal Veterinary College for several years. He became an attending physician at Montreal General in 1878. By the 1880s, with a hospital practice and his pathological studies, Osler had developed considerable knowledge of a wide range of diseases, and was increasingly called on as an experienced consultant.

During his Montreal years, Osler also took a great interest in the post-Civil War educational reforms in process at some American medical schools, especially at Harvard, and made several visits to the United States. At McGill, he advocated for the extension of clinical training, and modernizing of exams, among other changes. From the first, he was an active participant in local, national, and international medical societies, and a frequent contributor to the medical and biological sciences literature.

In 1884, Osler accepted the chair of Clinical Medicine at the venerable University of Pennsylvania School of Medicine, attracted by the broader clinical opportunities in Philadelphia. There he was responsible for clinical lectures, ward rounds, and autopsies. Although Pennsylvania did not have the clinical clerkship as a required part of its program, Osler and his students were able to see patients in the large Philadelphia Hospital complex and several specialty institutions. Osler also developed a thriving consulting practice, which included several visits to the poet Walt Whitman, who lived in nearby Camden, New Jersey. Osler became a popular instructor at Pennsylvania, made many good friends and professional connections, and joined several local medical groups, including the College of Physicians of Philadelphia. He began taking a role as "medical statesman" in presentations to medical societies, addressing professional questions such as the standards of medical schools and women as physicians.

In 1889, Osler moved to Baltimore to become Physician in Chief of the just-opened Johns Hopkins University Hospital and Professor of Medicine in the new medical school (which would open in 1893). At "the Hopkins" he was the primary architect of America's first modern medical training program, which was modeled on German teaching hospitals. In Osler's system, third-year medical students began working in the outpatient clinics, and fourth-year students worked the hospital wards in two-month rotations, under the supervision of the junior and senior medical residents who were responsible for the day-to-day business of each department. This intensive "teaching at the bedside" insured that new medical graduates had several years of practice with all kinds of cases, and were well-versed in the current medical practices, including clinical laboratory work. Osler's own teaching rounds in the wards were legendary, for their thorough exploration of each case as well as for Osler's genial, informal manner with both patients and students.

Between the time the hospital opened in 1889 and the opening of the medical school in 1893, Osler also wrote a new medical textbook, The Principles and Practice of Medicine, which brought together his own substantial clinical experience with the latest knowledge of disease and treatment, including the contributions of the fast-growing field of bacteriology. The textbook was a great success and remained an important reference for decades.

In 1892, just after finishing the textbook, Osler married Grace Revere Gross, the widow of Philadelphia surgeon Samuel W. Gross. They had two sons, one of whom died soon after birth. The other, Edward Revere (known as Revere) lived to be twenty-two.

As Johns Hopkins became America's premier model of medical education, Osler became the country's foremost clinical educator as well as a renowned diagnostician with a large consulting practice, a prolific author on a broad range of topics, and an active member of many professional groups. By 1900, he was one of the best-known physicians in the world. Although he loved his work in Baltimore, Osler's many activities became harder to juggle as he grew older and he began to think of retiring. When Oxford University offered him the Regius Professorship in Medicine in 1904 he accepted at once.

The Oslers moved to England in May 1905 and for nearly a decade enjoyed an idyllic life there. Osler gave degree examinations to Oxford medical graduates, held weekly clinics at Oxford's infirmary, and enjoyed working on various university committees, including those of the Bodleian Library and the Oxford University Press. He also spent more time building and cataloging his library, and writing studies in medical history. In 1911, King George V conferred a baronetcy (hereditary knighthood) on Osler, in recognition of his many contributions to medicine. The First World War brought an end to Osler's contented semi-retirement. During the war, he helped organize some of the military hospitals in the Oxford area and served as attending physician to several. The Osler home received a constant stream of visitors, military and civilian, and for a time housed refugees too. Like many of their friends, the Oslers lost their son to the war: Revere Osler was killed in Belgium in August 1917.

Sir William Osler survived his son by only a few years. In October 1919, several months after his seventieth birthday, he developed a respiratory infection--possibly secondary to influenza--which gradually worsened into pneumonia. He died on December 29, 1919. His cremated remains, and those of Lady Osler (who died in 1928), are interred within the Osler Library at McGill University.

Osler published well over 1300 original articles during his career, covering a wide range of medical topics. His earliest were drawn from his natural science and pathology studies, both human and animal. In clinical medicine and public health he wrote about almost everything except gynecology, obstetrics, and surgery: infectious diseases like typhoid, malaria, tuberculosis, and pneumonia; heart diseases, cancers, nervous system diseases, Addison's disease, diabetes, and more. His textbook The Principles and Practice of Medicine went through sixteen editions in fifty-five years. Many of his presentations and addresses on medical history, on medical education, on medicine as a vocation, and as a profession were also published, and later republished as collections.

Throughout his life, Osler was a self-described "bibliomaniac." His early mentors introduced him to a wide range of subjects and authors, both contemporary and historical, conveying their great enjoyment of these. Osler regarded himself as a lifelong student, and believed that broad and constant learning was a fundamental part of a life in medicine. Likewise, he believed that good libraries--including current literature and historical works--were essential to medical schools and to medical associations. An avid book collector with a large personal library, Osler took a keen interest in building the collections of the Johns Hopkins medical library and that of the Maryland State Medical Society, among many others. He helped to found the Association of Medical Librarians (now the Medical Library Association) in 1898, and served as its president from 1901-1904. Most of his own library, nearly eight thousand volumes, he left to McGill University, where it became the foundation of the Osler Library of the History of Medicine, opened in 1929.

Osler received many awards and honors during his career. He was elected to the Royal College of Physicians in 1878, elected to the Royal Society of London in 1898, and was made a baronet by King George V in 1911. Besides these were honorary doctorates from McGill University in 1895, the University of Edinburgh in 1898, the University of Toronto in 1899, Harvard and Oxford in 1904, and Johns Hopkins in 1905. Osler also identified a number of diagnostic signs, diseases and syndromes that now carry his name.

Much has been written about Sir William Osler, including two full-length biographies. For many years after his death, those he trained, worked with, and mentored wrote memoirs and reminisced about the great clinician. Perhaps the most striking thing about these accounts is that they often focus not on Osler's research or therapeutic or intellectual innovations, but on his character, his life philosophy, his example as a teacher, physician, and human being. Osler once said, "I desire no other epitaph than the statement that I taught medical students in the wards, as I regard this as by far the most useful and important work I have been called upon to do." For many, he is still the epitome of the physician as humanist.