Charismatic, warm, modest - and devilish with lemon slices

Sir William Osler glimmers across the consciousness of modern historians of medicine - the idolised clinician, author of the first great medical textbook, regius professor of medicine at Oxford University - a name that otherwise offers little of substance.

Osler made an enormous impression on almost all who encountered him during his life-time but his two great talents, as teacher and as practitioner at the bedside, were historically transient. They shaped no new directions in the flow of medical knowledge, or in the nature and organisation of medical practice. In retrospect, Osler seems somehow a bystander rather than a participant in the making of modern medicine. The monumental, hagiographic biography by his friend and colleague Harvey Cushing is unfashionable and rarely read. For those curious to investigate the nature of Osler's glimmering shadow, Michael Bliss's lucidly written biography offers an enjoyable entree into another world. For Bliss, Osler's story has a resonance beyond medicine, as a reflection on the human condition and "the quest for salvation and the forms of immortality".

Although there is necessarily a good deal about the practice, teaching, financing and modernisation of medicine in the later 19th century, the social context of that medical life is vividly evoked - evangelical Anglicanism in backwoods Canada, the panache of Victorian America, the flowers and fragrance of Edwardian Oxford and the impact of the first world war on non-combatants with friends in Britain, Canada and America.

Born in Upper Canada in 1849, Osler came to medicine via natural history. He studied at Toronto and McGill, did a medical grand tour of England, Germany and Austria, and returned to McGill as "the baby professor" in 1874. McGill made two things of Osler: a brilliant teacher, for whom the lessons of the bedside were part and parcel of the learning process, and a student of disease, for whom the observation and recording of disease formed the basis of medical diagnosis, the potential for treatment and the exercise of the clinician's art. From McGill he went to Philadelphia, and from there to be one of the founding professors of the Johns Hopkins medical school in Baltimore. Osler's skills as teacher and clinician helped put Johns Hopkins at the forefront of American medicine. He ran a vastly successful private practice, travelling thousands of miles a year to attend relatives, friends, colleagues and the more, or less, wealthy who requested his services. It was a life that increasingly exhausted him: "I am tired of the hunted life," he wrote in the early 1900s, worried that the pace of his life would destroy his health. From his middle years, he expressed the belief that a man was past his best by 40. In 1904, aged 55, he accepted the regius professorship as an opportunity to grow old gracefully.

Three intellectual phases can be distinguished in Osler's life. In his early years, he was above all a pathologist, spending all the time he could spare in the dead-house studying the manifestations of disease in cadavers. After the move to Philadelphia, the passion for pathology waned, and he focused his energies on writing case histories - a form of scientific communication that was looking increasingly old-fashioned by 1900. In semi-retirement at Oxford, bibliomania set in, and the collection, annotation and cataloguing of old medical books became his favourite pastime. Detailed observation was the hallmark of Osler's work. The same warmth of attention, given to whomever he was speaking, illuminated people's lives, fixed him in their memories, and formed the basis of his charisma.

The central problem with most medical biography and autobiography is a tendency to cast the doctor in the heroic mould, as saviour and saint. Bliss is painfully aware of this danger and manages to avoid it - just - through the exercise of restrained fair-mindedness. As any serious modern biographer would, he looks for Osler's feet of clay. In vain. Except for a persistently puerile streak in his sense of humour (even when dying he kept lemon slices at hand to lob into his visitors' hats), Osler was a delightful man - modest, amusing and humane. The real achievement of Bliss's biography is to demonstrate the part that the doctor's humanity played in the successful practice of medicine in the days before the therapeutic revolution. The moribund patient who murmured "Ah! Osler has come!" when given a shot of morphine spoke not only of his faith in Osler personally, but of the physician's role as comforter of the sick. The most telling vignette is that of Osler summoned from an Oxford degree ceremony to the bedside of a severely ill boy. He appeared in full academicals, to the delight of his patient, and administered sugared peach slices. Against expectation, the child rallied, and for the next 40 days Osler donned his scarlet robes for a daily examination.

Despite his profound pathological studies and his knowledge of symptom and physical stress, Osler believed in treating patients and not diseases. Therein lay his magic and the explanation for the dimming of his star, as those whose lives he personally touched have passed away.

Anne Hardy is reader in the history of modern medicine, Wellcome Trust Centre for the History of Medicine, University College London.