A few friends have asked the meaning of this blog’s sub-header, which reads “May I direct your attention to the curious incident of the dog in the night-time?” This is a paraphrase of a famous exchange in the Memoirs of Sherlock Holmes, one of my favorite passages in detective fiction. It combines two of my enthusiasms (dogs and detective stories), touches upon my professional work, and in a playful way illustrates a first principle of cautious thought.
Arthur Conan Doyle published the Memoirs of Sherlock Holmes in 1894. This was the fourth collection of Holmes stories, which began seven years before with A Study in Scarlet. The books gained phenomenal popularity, but by the 1890s Conan Doyle was a frustrated author. He believed his true calling was to write history, and the detective was a distraction. “I think of slaying Holmes. . . and winding him up for good and all,” he confided in 1891. “He takes my mind from better things.” And so in the last pages of the Memoirs, he sent Holmes careening from the cliffs of Reichenbach Falls, locked in deadly embrace with his archenemy Professor James Moriarty. They meet their fate “deep down in that dreadful caldron of swirling water and seething foam. . .”
(Of course, Holmes returns one day, but that’s another story.)
The incident of the dog in the night-time occurs near the start the Memoirs, in the tale entitled “Silver Blaze.” On a rainy night in the moorlands of southeast England, the champion thoroughbred Silver Blaze goes missing, just days before the running of the Wessex Cup. The horse’s trainer is found dead on the moor, his skull “shattered by a savage blow from some heavy weapon. . .” There is an abundance of evidence to consider: a stable boy drugged with opium, a gambler visiting in search of betting tips, a sudden illness among sheep, receipts from an expensive London hat-maker, a trampling of hoof prints in the soft earth near the corpse.
Among these perplexing clues, two greatly interest me. The dead trainer is found clutching a small weapon, “an ivory-handled knife with a very delicate, inflexible blade marked Weiss & Co., London.” Conan Doyle is having some professional fun here. Although he achieved fame as an author, his first career was medicine. He began as a general physician, but after a decade of lackluster practice, in 1890 he went to Vienna to study ophthalmology. He returned to England confident of success as an eye specialist. But by the time of the Memoirs in 1894, his medical hopes again were failing. Now back to the knife, which Holmes inspects with Dr. Watson:
“This is a very singular knife,” said Holmes, lifting it up and examining it minutely. . . “Watson, this knife is surely in your line?”
“It is what we call a cataract knife,” said I.
“I thought so. A very delicate blade devised for very delicate work. A strange thing for a man to carry with him upon a rough expedition. . .”
“It is what we call a cataract knife.” Watson’s statement is as incisive as the blade. The knife, Holmes explains, is “used for the most delicate operations known in surgery.” These lines make me smile. Conan Doyle the author is paying compliment to Conan Doyle the physician. Although his ophthalmology practice never flourished, he was proud of his medical skill. Ocular surgery, he knew, can demand a mix of intellect and daring, and so he treated himself to this commendation from the great Sherlock Holmes. Like Conan Doyle, I’m also an ophthalmologist, specializing in cataract and glaucoma surgery. He wouldn’t mind, I don’t think, if I too take encouragement from Holmes’s words.
Now to the dog. Mid-way through the tale, Holmes and a local policeman discuss the case. The facts begin to clarify in Holmes’s mind, but the policeman remains perplexed. Seeking insight, he asks Holmes, “Is there any point to which you would wish to drawn my attention?”
“To the curious incident of the dog in the night-time.”
“The dog did nothing in the night-time.”
“That was the curious incident,” remarked Sherlock Holmes.
The canine at issue is a stable dog who slumbered while Silver Blaze was stolen and the trainer was killed. How curious, Holmes observes, for a dog to sleep through such mayhem. He concludes that the thief and killer had been known to the dog, who otherwise would sound the alarm. Suddenly the circle of suspects shrinks. For Holmes, this absence of evidence is as compelling as a corpse.
The incident of the dog in the night-time is a famous display of Holmes’s reasoning and Conan Doyle’s skill. The concept of a negative clue is a powerful one. For me, it’s something I think about more or less every day at work. A woman presents with redness, swelling, and pain around the eye but no fever. A man complains of a blood-shot, aching eye but no discharge. A girl reports seeing halos around lights but denies nausea. For every problem, what is present may be as important as what is missing. Amid the commotion of illness or injury, we naturally focus on facts in plain sight: the new pain, the sudden change in vision, the worsening swelling. A careful approach is needed to observe the missing facts: the fever that never occurred.
A college professor once taught me that the historian is really a detective, assembling evidence from books, maps, photographs, journals, gravestones, and news clippings. This same view applies to medicine; there is a fundamental aspect of skeptical detection. Indeed, Conan Doyle’s model for Holmes was his medical school professor Joseph Bell, who emphasized observation, deduction, and inference in medical diagnosis.
The physician as detective: the idea is both accurate and romantic. Certainly it lends welcome flavor to otherwise dull hours over textbooks and late nights in the hospital. And so sometimes that is how I view myself, examining a diseased patient, plying some “very delicate blade devised for very delicate work.” I remember that Dr. Bell and Dr. Conan Doyle were here before. I listen for a dog that doesn’t bark.