William Osler became a physician at a time when medical practice and education were just beginning to incorporate scientific knowledge and experimental methods. During the preceding several centuries, the theoretical teachings of Galen and other traditional authorities had started giving way to a more direct approach to nature and medicine. As urban populations grew in the early 1800s, physicians treating patients in large public hospitals in Europe (especially Paris) could observe large numbers of patients with similar diseases. When those patients died (as they often did), their remains could be dissected and the condition of the tissues and organs correlated with the clinical symptoms. New techniques and tools allowed better observation of a patient's condition: percussing the body to hear characteristic changes in tissue density, auscultation (listening to the body, often with a stethoscope), taking the pulse, and measuring temperature with a thermometer. Clinicians began keeping statistics of cases, and gradually developed new descriptions of specific diseases from this work. (They were also able to show that many traditional treatments, such as bloodletting, were not helpful.) Some investigators also began correlating unsanitary conditions with the presence and spread of certain diseases in the hospitals and beyond.

By the 1850s, improved microscopes made it possible to study diseased tissues at the cellular level, and for pioneers such as Louis Pasteur to begin making connections between the presence of particular microorganisms and specific diseases. It would take several decades for these connections to be proven and widely accepted, but some, such as surgeon Joseph Lister, used the concept to reduce surgical infections starting in 1865. Chemical knowledge was also expanding rapidly, making available morphine from opium, ether for surgical anesthesia, and stains that could better reveal microbes and tissues under the microscope. The field of experimental physiology was growing too, and increasingly using animals for research.

Most medical schools in North America were not incorporating this exciting new knowledge into their programs. They were small institutions, founded by local physicians who served part-time as faculty. Some were loosely affiliated with universities. They typically offered a degree after two years of attendance at lectures in seven traditional medical subjects, and perhaps demonstrations. There was little or no laboratory work or anatomical dissection, and no direct attendance on patients. Entrance requirements might be nothing more than the ability to pay, as almost all the schools were proprietary, i.e., run by the faculty physicians to make money; rigorous entrance exams or other requirements would discourage customers. The profit margins were usually quite small, and the schools were often in financial straits.

A young medical student or recent graduate seeking practical experience could apprentice himself to an older doctor, or, in the larger cities, take a position as an unpaid "house officer" at a hospital; he could also travel to Europe's big medical centers for training. But these options required some financial means, and often social connections as well, and so were beyond the reach of many students. Thus there was considerable disparity in knowledge and skill among physicians, depending on their family income and social status. The American Civil War (1861-1865) had given thousands of physicians rigorous experience in surgery, hospital care, and recording case studies, and had highlighted the shortcomings of American medical colleges, but widespread reform would not be accomplished until after 1900.

The Toronto School of Medicine, where Osler began his medical studies in 1868, was perhaps a little better than average. Its faculty included several talented, well-educated physicians, including Osler's mentor James Bovell, and Dr. John H. Richardson, the professor of anatomy. Toronto's students also were provided occasional access to patients at the small Toronto General Hospital. Osler spent most of his time there in the dissecting room, or collecting specimens of polyzoa and diatoms to examine with Bovell's microscope. His first publication, "Christmas and the Microscope," published in 1869, described the many organisms he found on a Christmas morning field trip, and the following spring he published a major paper in Canadian Naturalist describing over 100 diatoms he had gathered. In his second year at Toronto, he also made a study of Trichinella spinalis parasites he had discovered in the tissues of trichinosis victims. When Bovell decided to leave Canada to return to his native West Indies in 1870, he advised his protégé to complete his medical training in Montreal.

The McGill Faculty of Medicine was one of the more advanced medical schools in North America. Modeled on the University of Edinburgh's medical school, it had high admission requirements for the time, longer teaching sessions, and a four year course rather than two. The curriculum strongly emphasized dissection, and students had access to a four thousand volume library and an anatomical and pathological museum. Several of the faculty had gone to Europe for additional training. McGill medical students were required to do at least twelve months of observation and assisting in the medical and surgical wards of the Montreal General Hospital, and with obstetrical cases at the Lying-In Hospital. Still, the school had no laboratories, and none of the faculty used a microscope in teaching.

Osler had a very busy two years at McGill. He attended lectures and continued his study of microscopic parasites when time permitted. Like all senior students, he served in the hospital as a clerk (pronounced "clark") and surgical assistant. Unlike some of his fellows, he also spent much time in the dissecting rooms. Following the British practice, clerks wrote up interesting cases for publication in the local medical journal. Osler's first medical publication in 1871 was about five cases attended by Dr. D. C. MacCullum, and included Osler's findings from examination of tumor sections from one patient and a full post-mortem on another. His primary mentor during these years was Dr. Robert Palmer Howard (1823-1899). A McGill graduate, Howard had studied in London, Edinburgh, Dublin, and Paris before joining the faculty in 1852. By Osler's time, he was professor of the theory and practice of medicine. He was an enthusiastic and excellent teacher, drawing not just on hospital practice, but on postmortem exams and his familiarity with the medical literature. He had a special interest in pulmonary disease, especially tuberculosis, and enlisted Osler's help in 1871:

Postgraduate Studies

Osler received his MD, CM [Chirurgiae Magister or Master of Surgery] in 1872. The faculty awarded him a special book prize for his original thesis, which was a series of twenty postmortem studies, illustrated with thirty-three slides and specimens. After graduation, Osler chose to pursue postgraduate studies in Europe. This was in part a practical decision: the McGill faculty wanted him to stay on as an instructor, but he would also need to have a medical practice to survive financially. Additional scientific and specialty training would give him an advantage both as a practitioner and as a professor. As no postgraduate programs existed in North America at the time, young physicians who could afford it went abroad for additional training. With financial support from his older brother Edmund (by then a successful financier), Osler went to London to study physiology and ophthalmology. He dropped his plan to specialize in the latter when he heard from Howard that several ophthalmologists were to open practices in Montreal. But he decided to continue his physiology studies, both to add to his credentials and to acquire the expertise he would need to persuade the McGill faculty to establish some serious laboratory facilities and courses.

Osler spent over a year working with John Burdon Sanderson, one of the great experimental physiologists of the era. Through Sanderson he was able to observe clinicians and surgeons at University College Hospital, and St. Thomas's Hospital, and meet a wide circle of physicians and scientists. In Sanderson's lab, he did a series of studies on white blood cells. In the process, he noticed colorless masses that were neither white nor red cells, and did a detailed study, which became one of the earliest identifications of blood platelets.

Although important medical work was being done in London in the 1870s, the forefront of scientific and clinical medicine was in Germany and Austria. In these countries Americans could study with outstanding scientists at highly organized, research-oriented universities and hospitals unlike any in the world. In October 1873, Osler moved on to Berlin, where he attended lectures and rounds at the large Charité Royal Hospital. He devoted much of his time in Berlin, however, to Rudolf Virchow's lectures and demonstrations at the Pathological Institute. Early in 1874, he went to Vienna and spent four months taking clinical courses in a wide range of subjects and gaining additional hospital experience at the vast (over 2,000 beds) Allgemeines Krankenhaus there. In both places he met many American and Canadian students, some of whom would become lifelong friends.

On the McGill Medical Faculty

Returning to Montreal in 1874, Osler accepted a post as Lecturer in Institutes of Medicine (which comprised the areas of physiology, histology, and pathology) at McGill, and was soon promoted to professor. He rapidly became one of the most popular faculty members; not just for his innovative teaching, but for his cheerful, informal manner and an uncanny ability to remember names and faces and to make all acquaintances feel like friends. Before the end of his second year, he had introduced new courses in histology (for which he supplied fifteen microscopes with his own money), 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. Many of the reports were published or presented at medical meetings. During his tenure at McGill, Osler did over a thousand of these post-mortem exams.

To supplement his small part-time faculty salary in these early years, he opened a small private practice, and served as attending physician to the temporary smallpox ward at Montreal General Hospital. He also taught pathology for the Montreal Veterinary College for several years. He did a number of studies in comparative pathology, including investigations of cattle diseases, and parasites in the pork supply of Montreal. In 1878, he became an attending physician at Montreal General, greatly increasing his (and his students') access to clinical cases. Even in these early years, Osler had adopted the highly organized work habits that made him a productive investigator, astute practitioner, and very well-read teacher of medicine.

As Osler biographer Michael Bliss notes, during the next six years, "Osler's energies, curiosity, and expanding clinical experience took him riding off in all directions." He investigated "pernicious anemia, Bright's disease, Hodgkin's disease, ulcerative endocarditis, tabes dorsalis, nephritis in pregnancy . . . tubercular meningitis, the histology of tumors, croup, muscular atrophy, fibroid phthisis, the impaction of gallstones, and more." He also became interested in brain diseases and did studies of brain tumors, cerebral hemorrhages and multiple sclerosis. He procured the brains of several executed criminals, to test the idea that criminal brains were visibly deformed (he concluded they were not). By the early 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. He also went back to Europe several times during the summer months, whenever his budget allowed, to do further scientific study. Despite his wide-ranging investigations and interest in scientific developments, Osler never considered himself primarily a scientist. As Bliss has noted, "his three broad interests were learning about the natural history of disease, teaching about disease, and doing what he could to treat it." Even in the 1880s, "he was much more interested in doing pathology than immersing himself in the new science that investigated life processes through extensive animal research."

Besides adding modern scientific pathology studies to the McGill curriculum, Osler also became a faculty reformer. He advocated for the extension of clinical training, and modernizing of exams, among other changes. He and his younger colleagues took great interest in the sweeping post-Civil War educational reforms then in process at Harvard under Charles W. Eliot, and made several visits to Boston, getting to know many of the leading academic physicians there. He was from the first an active participant in various medical societies--local, national, and international--as well as a frequent contributor to the medical, veterinary, and biological sciences literature. Likewise, he cultivated a wide circle of medical friends in Canada, the United States, Great Britain, and Europe. By the time he was made a fellow of the Royal College of Physicians in 1883, he was becoming better known for his achievements. Many of his McGill colleagues expected he would get a better offer at some point, and in 1884, he did.