“I take it, in the first place, that neither of us is prepared to admit diabolical intrusions into the affairs of men. Let us begin by ruling that entirely out of our minds.”
—“The Adventure of the Devil’s Foot”
In an article by Harold Billings on the subject of medicine in the Holmes canon, there is a long biographical aside, describing a letter that Conan Doyle, still a medical student, contributed to the British Medical Journal in September of 1879, which carried the title ‘Gelseminum as a Poison.’ Billings notes:
This letter… is a record of Conan Doyle’s attempt to find the limits to which the drug could be taken before one suffered serious side effects…“Several years ago,” he wrote …“a persistent neuralgia led me to use the tincture of gelseminum to a considerable extent. I several times overstepped the maximum of the text-books without suffering any ill effects. Having recently had an opportunity of experimenting with a quantity of fresh tincture, I determined to ascertain how far one might go in taking the drug, and what the primary symptoms of an overdose might be.” He increased the amount of drug on a daily basis, well past the point usually suggested as a limit, until “diarrhoea . . . [became] so persistent and prostrating” that he gave up the experiment.
Billings rightly attests that this missive not only telegraphs behavior Conan Doyle would later attribute to Holmes, but was actually not uncommon within the context of Conan Doyle’s own schooling at the University of Edinburgh. He notes two likely sources of inspiration: Sir Robert Christison, Professor of Medicine and Therapeutics, who, while already nearing retirement in Conan Doyle’s first year, was well-known for experiments with dangerous drugs, on both himself and his students, of which Conan Doyle was doubtless aware. A second prominent inspiration would be Christison’s student and successor, Sir Thomas Richard Fraser. It was likely that these noted scholars and scientists, as well as his own experiences in self-experimentation, would cement the idea in his mind, later to appear in “The Adventure of the Devil’s Foot.”
Use of his medical and scientific knowledge—from “The Resident Patient” to The Hound of the Baskervilles greatly enhanced the exoticism of his stories. “The Adventure of the Devil’s Foot,” despite its hints (summarily dismissed by Holmes) as something more supernatural, is no exception. Billings states that “the “devil’s-foot root” could have been inspired by what Conan Doyle knew of gelseminum, prepared from the twisted, “tortuous” root of the Yellow Jasmine.” And Holmes and Watson’s risky, death-defying experiment would no doubt hearken back to Conan Doyle’s own early chemical adventures. This triumph of empiricism could be construed as a tribute, of sorts, to the profession that led him to his literary fame—and would certainly make his early role-models—Bell, Christison, and Fraser—smile knowingly.