John James Rickard Macleod (1876–1935)

From Aberdeen to Toronto: building a career in metabolism

Macleod was not a Toronto outsider parachuted into the insulin story — he arrived there in 1918 as one of the most credentialed physiologists of carbohydrate metabolism working anywhere. Born in Clunie, Perthshire, the son of a Free Church of Scotland minister, he grew up in Aberdeen and took his medical degree there with honours in 1898 before pursuing advanced biochemical training in Leipzig, then a world centre for physiological chemistry. By the time Frederick Banting walked into his office in November 1920, Macleod had already spent fifteen years at Western Reserve University in Cleveland studying carbohydrate metabolism specifically, had published six monographs and numerous papers, and was internationally regarded as an authority on the biochemistry of diabetes — a disease that, before insulin, was a death sentence for anyone diagnosed as a child, managed only by starvation diets that bought a few extra years of suffering.

This matters for how the discovery is properly understood. Banting arrived with an idea and clinical intuition but no significant laboratory research experience, no funding, and no institutional standing. What Macleod supplied was not incidental — it was the entire scientific infrastructure the project needed to succeed: laboratory space, experimental animals, a trained research assistant in Charles Best, instruction in the difficult Hédon pancreatectomy surgical technique, and, crucially, the scientific judgment to demand that early, promising-looking results be rigorously repeated and verified before being believed.

Summer 1921: absence, autonomy, and the roots of resentment

Macleod left for a summer trip to Scotland shortly after agreeing to support Banting's project, leaving Banting and Best working largely on their own through the summer of 1921. It was during this period that the two men achieved their first striking results — extracts from degenerated pancreatic tissue that lowered blood sugar in diabetic dogs. This arrangement, seemingly a matter of simple scheduling, became the seed of the entire later controversy: because Macleod was not physically present for the breakthrough experiments, Banting came to feel — and later argued publicly and repeatedly — that the discovery belonged to himself and Best alone, and that Macleod's subsequent involvement amounted to a senior academic claiming credit for junior researchers' work.

That framing does not survive contact with the full record. Macleod's skepticism on his return in September 1921 was not obstruction; it was exactly the kind of rigorous demand for reproducibility that separates a genuine discovery from a false positive — and it was Macleod who insisted the results be repeated before anyone went further. More decisively, it was Macleod who, in December 1921, recruited biochemist James Collip to the team. Collip's contribution — refining the crude pancreatic extract using alcohol purification — is what turned an inconsistent, sometimes toxic preparation into a reliably safe treatment that could be given to human patients. Without Collip's purification method, brought in at Macleod's initiative, insulin as a usable medicine would very likely not have existed on the timeline it did. Macleod also personally oversaw the coordination of the first clinical trials at Toronto General Hospital in January 1922, and it was Macleod, not Banting, who negotiated the pivotal May 1922 manufacturing agreement with Eli Lilly and Company that made mass production possible.

A presentation, a breakdown, and a grievance that would not fade

One specific incident crystallised Banting's anger and has been retold, with varying accuracy, in almost every popular account since. In December 1921, the team presented their findings to the American Physiological Society at Yale. Banting, inexperienced as a public speaker and deeply nervous, faltered badly during his portion of the talk. Macleod, an experienced and polished lecturer, stepped in to complete the presentation. Banting experienced this — not unreasonably, from his own perspective, though the historical record does not support his conclusion — as Macleod seizing an opportunity to present himself as the discovery's leading figure. He later described it as "a brazen coup by Macleod to rob him of the credit." This single episode became, in Banting's retelling over the following two decades, a symbol of a much larger claimed injustice.

The Nobel Prize and its long aftermath

In autumn 1923 the Nobel Committee awarded the Prize in Physiology or Medicine jointly to Banting and Macleod — not to Best or Collip, a decision that has itself been debated by historians of science, but one the Committee justified explicitly on the grounds that, in its own words, Banting would not have found the way to insulin without Macleod's guidance. Banting was reportedly so outraged that he initially considered refusing the prize altogether; he ultimately accepted it but split his prize money with Best. Macleod, for his part, split his own share with Collip — a detail that receives far less attention in popular tellings than Banting's gesture, but is equally well documented and equally telling: both men used their prize money to correct what they each judged to be an incomplete piece of institutional recognition.

Banting's resentment did not fade with the award. He spent much of the rest of his career, until his death in a 1941 plane crash, actively working to diminish Macleod's role in both scientific and popular accounts of the discovery, and Charles Best continued this effort after Banting's death. The University of Toronto, wary of reopening a bitter internal dispute involving two of its most celebrated figures, kept much of the relevant archival documentation restricted for over fifty years. As a direct consequence, the version of the insulin story that dominated public memory for most of the twentieth century — Banting and Best as the heroic discoverers, Macleod as a credit-claiming administrator who happened to be in charge of the lab — is now understood by historians to be a significantly distorted account, shaped less by evidence than by the surviving grievance of one party and decades of restricted access to the other side's records. A 1976 television dramatisation, "Comets Among the Stars," depicted Macleod in explicitly unflattering terms, reflecting and reinforcing this one-sided narrative; it was not until archives opened following Best's death, and a more balanced 1988 film treatment, "Glory Enough for All," that a fuller picture reached a wider audience.

Leaving Toronto, returning home

By 1928, the atmosphere at Toronto had become personally difficult for Macleod, and he returned to Scotland as Regius Professor of Physiology at the University of Aberdeen — succeeding his own former teacher, John Alexander MacWilliam, in the chair. Banting's hostility by this point was such that he refused to attend Macleod's farewell dinner in Toronto. Rather than remaining in the field that had made him famous, Macleod largely moved on from insulin research in Aberdeen, pursuing wider questions in carbohydrate metabolism, including work on teleost (bony) fish that helped demonstrate insulin's origin in the islet tissue of the pancreas rather than the surrounding acinar tissue, and research supporting his long-standing view that the central nervous system plays a significant regulatory role in carbohydrate metabolism.

Later years and death

Macleod remained scientifically prolific throughout his life, authoring more than 200 papers and eleven books, including the widely used textbook "Physiology and Biochemistry in Modern Medicine," which reached its seventh edition in 1934. He served on the UK Medical Research Council from 1929 to 1933 and undertook a US lecture tour as late as 1933, despite worsening arthritis that increasingly limited his mobility in his final years. He died in Aberdeen on 16 March 1935, aged 58.

• Macleod never conducted the original insulin-extraction dog experiments himself — he was in Scotland on a summer visit when Banting and Best achieved their first key results in his laboratory.
• The word "insulin" itself was Macleod's suggestion for naming the extract.
• Banting was so angry about sharing the Nobel Prize with Macleod that he split his own prize money with Charles Best in protest — a fact usually told on its own, without noting that Macleod did the exact same thing, splitting his half with James Collip.
• Banting refused to attend Macleod's own farewell dinner when Macleod left Toronto to return to Scotland in 1928.
• The University of Toronto kept key documents relating to the insulin dispute restricted for over 50 years, meaning the popular version of the discovery story was shaped largely by one side's account for most of the twentieth century.
• It was Macleod, not Banting, who personally negotiated the landmark 1922 agreement with Eli Lilly and Company that turned insulin from a laboratory extract into a mass-produced, worldwide medicine.
• Macleod suffered from severe arthritis in his final years but still undertook a lecture tour of the United States in 1933, two years before his death.
• A 1976 television drama portrayed Macleod as "dark and repulsive" — a characterisation historians now regard as a product of the one-sided narrative that dominated for decades, not of the evidence.

The dominant popular myth here is not a single false anecdote but a decades-long distortion of emphasis: the "Banting and Best discovered insulin, Macleod took the credit" narrative that shaped public understanding for most of the twentieth century. This card does not treat that narrative as simply wrong — Banting's frustration was genuine and his and Best's experimental work was real and essential — but it does not accept it as the complete or balanced account either. The Nobel Committee's own stated reasoning, Macleod's documented scientific direction and recruitment of Collip, his coordination of clinical trials, and his negotiation of the Eli Lilly manufacturing agreement are all independently verifiable and support a more equal four-way (Banting, Best, Collip, Macleod) picture of the discovery than either the original popular telling or a simple reversal crediting Macleod alone. Readers should also note that the question of whether Best and Collip were unjustly excluded from the Nobel Prize itself remains a genuinely open historical debate, not one this card resolves.